Add the ability to request SUPL neworks.

Also:
 - Refactor the code to remove duplication and make it easier
   to add/change the network buttons.
 - Make the MMS network request specify TRANSPORT_CELLULAR as
   well, since that's what the system MMS service uses.

Change-Id: If8e2ca1ae22b3da3fffb0593fbb93a1d479143f3
3 files changed