Implement queue management in RewriteMediaManager

[nielsvanvelzen]

So I found out that I didn't implement this yet a week ago... oops. Also found (and fixed) some bugs while working on it.

Changes

• Support custom areItemsTheSame and areContentsTheSame functions in MutableObjectAdapter
• Implement queue management in RewriteMediaManager
  • Adding to an existing queue will always add after the current playing item (or current if no item is playing)
  • Adding to an empty/stopped queue will play immediately
  • I deliberately did not look at the old implementation for this behavior and used what made the most sense to me
• Optimize queue->currentAudioQueue sync
  • Use AudioQueueItem instead of BaseRowItem so the KeyProcessor shows the correct menu items for queue management
  • Simplify the mapping
  • Use custom areContentsTheSame function that always returns false to fix issue where the UI shows invalid data because the equals function in AudioQueueItem/BaseRowItem only checks the item id

Issues

!! #1057 !!