Background task management

[Avid29]

The app should have four states for background states

• Regular:
  No background tasks. The app is not connected to any voice channels.

• Voice Connected:
  Gateway and Voice run from in-process background task that can continue even when the app is suspended

• Closed w/ Notifications:
  When the app closes an out-of-process task begins that runs a watered down client to give notifications. No voice channels

• Closed w/o Notifications:
  The app is closed and no background tasks are running (except Rich Presence)