AppOps: track op persistence by name instead of id

On XML write, include the op name.  On XML read, map
the name back to op id (if it exists).

Persistent AppOp state now follows the op name instead
numeric id.  This means you can upgrade between
versions of CM and the op number does not matter.
Handy when merging with future android code drops
(CM AppOp ids might be used by Google).

Change-Id: Iffc02095b6838a34ff999f8db51c2c6739dd0db8