Initial Song Deletion

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This PR adds the Ability to delete Songs (from Disk permanently), but you will need to re-add your current Source Folders for writing Permissions.

Limitations/Missing/TODOs:

• You currently can only delete one song at a time, but album/artist/etc deletion should be easy to implement
• The deletion function has a write perm check that isn't tested and might create an Exception (might be candidate to delete)
• I'm not 100% certain whether the RadioQueue.removeAll() logic is fine as-is -> should be re-checked
• Some Repositories don't get updates that they would need (see TODOs in code, i personally don't mind whether the artist album count is correct after deletion, some will) -> potential for NPE's
• Logging still in Code
• i18n missing
• The DeleteSongDialog has "Details" as title, as the Structure is copied from the song information dialog