Bludit: Note if theme or plugin is not (yet) compatible

[clickwork-git]

As extension to the compatibility field in metadata.json there could be perhaps a note in the backend if a theme or a plugin is not (yet) compatible to the installed version.

[AbrahamAriel]

There should be a notice at the theme listing. User should be allowed to enable them if they still want to use an incompatible theme.

[anaggh]

I think the incompatible theme/plugin should have a warning with a light red background color instead of hiding it completely. :D

"_This theme/plugin is incompatible with your Bludit version. Proceed at your own risk."_

[dignajar]

Implemented on the Github version!