Added three new settings for compact mode

[sanjacob]

I wanted these customisations on my system for aesthetic purposes.

• Option to set fixed widget width (therefore not moving the entire row of other widgets when I close the music player).
• Option to hide Play/Pause button in track info and seek bar layouts.
• More track info format options (Track - Artist, Artist - Track, Track Only, Track by Artist (lowercase)).

Translations are needed for the new items in the settings menu and the lowercase 'by' track info format.