add in custom boot animation prefs

also add in the ability to restore previously set custom animations. some of the animation
preview was borrowed from AOKP.

PS2: cleanup
PS3: minor fix
PS4: attempt file channel RW access
PS5: assign animation path to root of sdcard and add permissions

Androidx:
Removed no bootanimation choice from original commit
Added needed manifest perms for AndroidxSettings app

Change-Id: Id6e8ac97a67fb4619839555512ef285c488a0562

Conflicts:
	res/values/vanir_arrays.xml
	res/values/vanir_strings.xml
	res/xml/system_ui_more.xml
	src/com/android/settings/vanir/AdditionalSystemUI.java