Made preference keys public in Preferences. PickServerFragment now compares preference keys when clicked instead of storing and comparing preference references.
Added presets preferences
Added another preference screen to choose the UI buttons. The UI does not yet implement these button preferences. Added icons for audio and subtitle delays and preset toggles.
Added audioDelay and subtitleDelay commands to media server
Implemented the button preferences
Reverted parts of commit 66ece6a and a77a0ac that implemented previous/next chapters. I overlooked simply using vlc's hotkeys to send as a command. This has the advantage of being available from vlc 2.0.0 instead of the original commits requiring api features from vlc 2.1.0+
Added previous/next chapter as a button option in preferences