Use form-action for event preview
Inline EventAdd::removePreview()
Merge branch 'master' of github.com:denkmal/denkmal.org into issue-209

Conflicts:
	library/Denkmal/library/Denkmal/Form/EventAdd.js
Merge branch 'master' of github.com:denkmal/denkmal.org into issue-209
Adjust docu
Upgrade to CM 1.15.5
Add preview for admin event form
Merge pull request #209 from njam/issue-209

Admin: Event editing form: preview?