[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
[2/3] Telephony: Flip to Mute/Reject Call

Call Settings - add menu entry

PS2 - PS4: Code Cleanup

Base: https://gerrit.omnirom.org/#/c/4668/
InCallUI: https://gerrit.omnirom.org/#/c/4669/

Change-Id: Ic011c5b9e10439fc900b1302f7e07dde494b2e5b

Conflicts:
	res/values/custom_strings.xml