Add notification email

[rsmith013]

Needs to be configurable to allow the user to choose what events they are notified about. Possible events:

• Date updated on grants claimed by user data centre
• Unassigned grants come in with label x
• New grants available with facility x

Also combinations. e.g.

• New grants with facility x AND New grants with facility y
• Field updated on grants claimed by user datacenter AND New grant with label x AND New grant with label y