[mbpi] Fix giffgaff uk mvno apn settings

Details got from an end user.
[mbpi] Add O2 UK MMS settings

There was no MMS settings for O2 UK so adding an entry of some
settings that were found. Previously there were some O2 settings
under GiffGaff UK MVNO section.
Merge pull request #27 from tkenakka/giffgaff

Giffgaff UK (mvno) and O2 UK settings updated