[FEATURE] Adds possibility to add and remove tags

* Add or remove tags in edit view
* Tags displayed in detail view
* Tags as keywords in meta field

For testing:
You need to set the view in the flexform of the BE plugin to get the removeTag action working.

Change-Id: I012c3b0daadc8cec26850446be0b6d7dda895810
Resolves: #51603
Reviewed-on: https://review.typo3.org/26534
Reviewed-by: Thomas Löffler
Tested-by: Thomas Löffler
[BUGFIX] Add additional classes to admin form

Resolves: #54418
Releases: 4.5
Change-Id: I0b6b9ce944aa9d11054afbdf70861b985818d779
Reviewed-on: https://review.typo3.org/29823
Reviewed-by: Thomas Löffler
Tested-by: Thomas Löffler