Custom carrier text (1/2) thanks a bunch @rukin5197

this was based on by AOKP's use of the code
enter nothing in the text box to revert back to default.

change to original commit:
- better integration into our wifi label feature in SystemUI

Change-Id: Ib24e476d4b83abd4f5b127ed1e4addfad517462d

Conflicts:
	core/java/android/provider/Settings.java