Migrate notification functionality to cloud functions

[aphexcx]

From @aphexcx on January 10, 2016 1:38

• Cloud function to claim pickup request, add donor id to volunteer's ACL, and send notification to donor
• Cloud function to confirm volunteer, add volunteer id to donor's ACL, and send notification to volunteer User ACLs prevent other volunteers from accessing user objects #2
• Cloud function to pickup donation; create donation object, and send notification to donor
• Cloud function to mark donation as complete (after congratulatory dialog is dismissed), remove donor id from volunteer ACL, remove volunteer id from donor ACL, and set pickupRequest as inactive.

[aphexcx]

• Testing on API18 device

[aphexcx]

@mkulumadzi Take a look and check that all of these are implemented on the iOS side.

[aphexcx]

• Testing with iOS