improved docs and cross-linked docker (#383)

var/docs/README.md

@@ -11,20 +11,18 @@ try to add it as soon as possible.
 For the most parts Kimai usage should be self-explanatory, so we will only cover topics here which were 
 [requested](https://github.com/kevinpapst/kimai2/issues) by the community.
 
-- [Timesheets](timesheet.md) - information about timesheets
-- [Invoices](invoices.md) - export your data to different formats with customizable templates
-- [User and Security](users.md) - docu for user and security topics, like authentication, registration and roles  
 - [Configurations](configurations.md) - intro into the global application configs
-    - [Emails](emails.md) - transport configuration and handling of emails 
-    - [Dashboard & widgets](dashboard.md) - how to configure widgets and dashboard sections
     - [Calendar](calendar.md) - the Timesheet calendar view
-- [Developer docu](developers.md) - how to extend Kimai's feature set  
+    - [Dashboard & widgets](dashboard.md) - how to configure widgets and dashboard sections
+    - [Emails](emails.md) - transport configuration and handling of emails 
+- [Developer](developers.md) - docs about extending Kimai's feature set  
+    - [API](developers_api.md) - how to use the JSON API 
     - [Theme settings](theme.md) - theme related settings
 - [FAQ](faq.md) - some answers to frequently asked questions 
-- [API](developers_api.md) - how to use the JSON API 
-- [Translations](translations.md) - all about languages and translations
-
-## Installation
- 
 - [Installation](installation.md) - instructions about several installation methods
-- [Importing data](migration_v1.md) - how to import your timesheets from Kimai v1
+    - [Docker](docker.md) - using the built-in Dockerfile for development
+    - [Importing data](migration_v1.md) - how to import your timesheets from Kimai v1
+- [Invoices](invoices.md) - export your data to different formats with customizable templates
+- [Timesheets](timesheet.md) - information about timesheets
+- [Translations](translations.md) - all about languages and translations
+- [User and Security](users.md) - docu for user and security topics, like authentication, registration and roles  

var/docs/installation.md

@@ -5,17 +5,43 @@ installation instruction in our [README](https://github.com/kevinpapst/kimai2/#i
 
 You need GIT and [Composer](https://getcomposer.org/doc/00-intro.md) on the machine where you want to install Kimai. 
 
-## Installing on a personal computer (instead of a server)
-### 1. No need to use www-data user
+## Docker
+
+There is a dedicated about [our Docker setup](docker.md), which is primarily meant for use in development. 
+
+## Installing on a personal computer
+
+### Which user to use - no need to use www-data user?!
+
 The installation instructions are intended primarily for server applications. 
-If you are installing Kimai 2 on a desktop or laptop computer - even for use in a local network, but where the computer primarily serves as a single user computer - you will avoid permission errors by subsituting ```www-data``` in the relevant commands with your username.
-In particular, ```sudo -u www-data``` is a command which grants the ```www-data``` user temporary administrator/super-user privileges). However, depending on the configuration of your particular computer, you may be able to avoid sudo altogether (your user may already have adequate permissions).
-You can try first leaving ```sudo -u www-data``` altogether in the relevant commands. If you have permission errors, you can substitute it for ```sudo -u username``` in the relevant commands (where username is the username that runs the server - if you don't know, it is likely your own username that you login with).
 
-### 2. Chown & Chmod commands
-Further, chown & chmod commands should be for the username that runs the server instead of ```www-data``` (again, if you don't know, it is likely your own username).
+If you are installing Kimai 2 on your personal computer - even for use in a local network, but where the computer primarily 
+serves as a single user computer - you will avoid permission errors by subsituting `www-data` in the relevant commands with your username.
 
-Also note that, depending on where you are installing Kimai 2 and how your computer is configured, you may also receive "operation not permitted" errors when setting file permissions (chown and chmod commands). In that case, prefix them with ```sudo ```.
+In particular, `sudo -u www-data` is a command which grants the `www-data` user temporary administrator/super-user privileges). 
+However, depending on the configuration of your particular computer, you may be able to avoid sudo altogether (your user 
+may already have adequate permissions).
+
+You can try first leaving `sudo -u www-data` altogether in the relevant commands. 
+If you have permission errors, you can substitute it for `sudo -u $USER` in the relevant commands (where username is the 
+username that runs the server - if you don't know, it is likely your own username that you login with).
+
+### chown & chmod commands
+
+Further, `chown` and `chmod` commands should be for the username that runs the server instead of `www-data` (again, if you 
+don't know, it is likely your own username).
+
+Also note that, depending on where you are installing Kimai 2 and how your computer is configured, you may also receive 
+"operation not permitted" errors when setting file permissions (chown and chmod commands). 
+In that case, prefix them with `sudo`.
+
+### Still doesn't work?
+
+These infos were added to give you some possible guidance if you run into troubles. The Linux (and Mac) filesystem 
+with its permission structure, especially when using server software, can be tricky and challenging.
+
+But this has NOTHING to do with Kimai and we might not be able to help you in such situations ... it is your system and 
+responsibility, be aware that wrong permissions might break Kimai and can also lead to security problems.
 
 ## Hosting & 1-click installations