actually care for the map music switch
don't hide the pause button after unpause
merge C&C and RA music player logic

mainly code cleanup, but with the following improvements:
- scroll to current song which fixes #3360 and overlapping label
- use Rules.InstalledMusic & Sound.MusicPlaying everywhere
- separated C&C install logic and log catched exceptions
- save the music settings on back/close
Merge pull request #3600 from Mailaender/music-player-fixes

Fixed various music player problems
Fix DescAttribute fail in CashTrickler.cs
Change IRenderable.WithPos -> OffsetBy.

This is more appropriate for the actual use cases.
Fixes #3621.
Don't render contrail shadows.
Merge pull request #3623 from ScottNZ/desc

Fix DescAttribute fail in CashTrickler.cs
Merge pull request #3624 from pchote/renderable-fixup

Renderable fixup
display IP, ping, jitter in in-game stats GUI

closes #2281
try to measure how often a client lags behind

clarify network stats labels and avoid overlapping for values
fix network stat headers not shown
don't display -1 pings for bots
don't count ping/pong for player APM