- Created audio device manager which manages weak ref handles to audio devices
- Audio device handles are created with WorldContexts and accessed through UWorld objects
- All access to audio devices are now through audio device handles
- There is a main/default audio device for GEngine for use with the Editor and single worldcontext games
#codereview marc.audy, matthew.griffin
[CL 2477046 by Aaron McLeran in Main branch]
Removed GVolumeMultiplier and added an equivalent to FApp to contain the code to load the unfocused volume multiplier from config.
UE-4449 - Allow users to choose whether audio can be heard when focus is lost
#codereview Robert.Manuszewski
[CL 2341022 by Matthew Griffin in Main branch]
