Improving album sharing feature

[crspybits]

1. Accept sharing invitation, existing account, doesn't refresh Albums screen: Accept sharing invitation, existing account, doesn't refresh Albums screen. #151

2. Make a sharing modal to improve sharing facilities:
   a) Number of people allowed to receive/accept invitation
   b) Permissions: read; read & change; read, change & invite
   c) Allow social acceptance-- inviter will host files
   d) help information on concept of sharing

3. Sharing email should include a link to download Neebla

4. Should show duration of expiry of sharing invite link(s) in the email