If an extension author adds an flattr url to the extensions metadata
gPodder shows the "Flattr this" menu entry in the popup menu for an
extension in the preference dialog.
Alternative the extension author can add an url to the extensions
metadata to link to the authors donation page (Support the author).
Also the extension author can add an url to the extensions metadata
to link to the extensions user documentation.
- Add category metadata in every extension
- Show this category in the extension list gui
- Add "mandatory_in" and "disable-in" configuration for an extension
- Add Ubuntu unity check to enable/disable unity specific extensions
- Move "gpodder.win32" and "gpodder.osx" setting to the "gpodder.ui" namespace to be able to use it in the extensions category settings
- Only show metadata information in the right-click dialog of an extension
