i9305: user configureable voice/streaming volumes

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.
(based on http://review.cyanogenmod.org/#/c/43834 by Scott Brissenden)

Change-Id: Ia4d9793786303156895b3f76b9e3a7831848b062
Requires: http://review.cyanogenmod.org/#/c/44098
DeviceSettings: fix overlay

Change-Id: I289722ab842d1b680f780cba2c9e1c85e6f74b5b