Camera2: Headset shutter mode

Use play button on headset to take a picture/video/panorama
Use media next/previous for zoom

Change-Id: I25c22646b041e5e0941fbe361eccfe77a2a1e42f
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_packages_apps_Camera2 into cm-11.0