Mobile Network Battery Saver Mode

When idle (screen off) switching to 2G can help extend
battery life as 2G generally uses less power than 3G or LTE.

    + 30 seconds after screen turns off, set network type to 2G
    + If a music player is active (playing), do not set network to 2G
    + When device is unlocked, reset to orignial network type

Settings -> More -> Mobile Networks -> Battery saving mode
[2/2] Telephony: allow disabling call end sound

Also remove the category around the intrusive
incall settings since more settings are added
below and this looks then strange

PS7
correct defaultValue

Change-Id: I37477582ecb3a8b74eb80db351401d83aab92b82

Conflicts:
	res/values/custom_strings.xml