added FAQ and database requirement docu #196 (#210)

* added FAQ and database requirement docu - fixes #196
* added FTP installation docu - see #199
* moved migration guide from Kimai v1 to its own docu chapter

var/docs/faq.md

@@ -0,0 +1,32 @@
+# Frequently asked questions
+
+## I have only FTP available ...
+
+So you want to install Kimai v2 but have no SSH access to your server? 
+There is a workaround available, read the additional [installation instructions](installation.md). 
+
+## Error on bin/console doctrine:schema:create
+
+If you get an error during the installation of the database schema that mentions `DC2Type:json_array`, e.g. like the following: 
+
+```
+In PDOConnection.php line 109:
+
+  SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'JSON
+   NOT NULL COMMENT '(DC2Type:json_array)', UNIQUE INDEX UNIQ_B9AC5BCE5E237E06' at line 1
+```
+
+Then the most likely case is that you are using a MariaDB database which is too old. You can find out which version is 
+used by executing `mysql --version` or by checking the server information e.g. with PHPMyAdmin.
+
+There is a [discussion in the issue tracker](https://github.com/kevinpapst/kimai2/issues/191) about this topic.
+
+There are two solution for this: 
+
+- Update your MariaDB server to at least 10.7.2
+- Switch to SQLite (that can be changed in your `.env` file)
+
+Further readings:
+
+- [MariaDB - JSON support was added with 10.7.2](https://mariadb.com/kb/en/library/json-data-type/)
+- [Using JSON fields with Doctrine ORM on PostgreSQL & MySQL](https://symfony.fi/entry/using-json-fields-with-doctrine-orm-on-postgresql-mysql)