t0lte: user configureable voice/streaming volumes [1/2]

This uses 4 files to store the voice volume:
incall_earpiece, incall_headphone, incall_speaker, incall_bt, and 2
for streaming volume: out_speaker, out_headphone located /data/local/audio.

Change-Id: I4269dc65d48e04b5e908b20704128241683d5a80

Conflicts:
	audio/audio_hw.c
t0lte: fix overlays for DeviceSettings

Change-Id: Ic76007839788532f97e9e5a122f94eb50438677d