group and contact list fixes

1) Updating a group without changing the avatar will keep that
   avatar

2) Prohibit adding non-push users to an existing push group

3) Add Android contacts to the same database. Takes a small amount
   more time and memory, but allows queries to not be a hack, and
   enables us to dedupe numbers in JB and higher devices.

Memory testing with my decently large contacts list only showed the SQL database taking up about 150k memory, so not much of an increase. Tested on GB as well, and the fallback to the non-normalized number appears to work just fine.