Apply thumbnail-settings on 'Album-covers' [#3924],
Bugfix for [#3927],
Added missing /div to thickbox-template,
fixed an issue with generating thumbnails when no thumbs
available in ImageManager,
improved the naming of thumbs,
Bugfix for [#3931],
Prevent display the content of galleries that are set as inactive.
Added an 'apply'-button to template editor