Remove unused settings constants from the SDK (framework).

The settings constants for various volumes do nothing and are
used by nothing since API version 2. These are however backed
up in the cloud which is a waste of resource. This change
removes these constants from the SDK while keeping them hidden
to avoid breaking released apps and also prevents unnecessary
backup.

Change-Id: I2e91863115f5a4b997a14f8d0f57b4dc9689cfab