Initial frontend-backend integration

Initial commit.
User groups are hardcoded.
Have not tested MessageActivity through the pre defined groups.
ContactsActivity takes a long time to load, have hardcoded the list of
contacts to be fetched from the phone.
Backend part of MessageActivity barely works.
Locations in LocationActivity are not fetched from the database.
Users are also added manually.
This may be the hackiest code I have ever committed.