As the old birthday resource is one of the major troublemakers with the compat bridges, port it from KResource to Akonadi.

It basically works but has a few known issues:
- birthdays of deleted contacts are not removed, needs fixing in Akonadi::ItemSync
- the category selection widget has been replaced with a KEditListBox to avoid dependencies from kdepim-runtime on libkdepim and kaddressbook, needs moving of the category stuff to kdepimlibs
- merging of anniversaries is not yet implemented