enhanced plugin support (#634)

- refactored admin controller and templates
- plugin support for entity actions
- changed column mail to email in customer table
- refactored theme events

config/packages/doctrine.yaml

@@ -31,3 +31,8 @@ doctrine:
                 dir: '%kernel.project_dir%/src/Entity'
                 prefix: 'App\Entity'
                 alias: Kimai
+            loggable:
+                type: annotation
+                alias: Gedmo
+                prefix: Gedmo\Loggable\Entity
+                dir: "%kernel.project_dir%/vendor/gedmo/doctrine-extensions/lib/Gedmo/Loggable/Entity"