GitLab

This pulls accessibility settings (which are not SIM-dependent) from
CallFeaturesSettings to their own Activity.

+ Added Accessibility settings activity and fragment.
+ Moved logic from CallFeatureSettings to new activity.
+ Defined a new file for constants pertaining to settings.

Bug: 19372734
Change-Id: I12d03c6c97c4573641c075a856dcc68260a579b8