Adding contact photo into notification message

[kcherenkov]

Like in the picture:

This feature should be optional, because there are some cons:

• It requires additional permission for managing contacts via Google API
• It requires two more requests for retrieving photo
• It increases traffic usage

Some info:

• Google Contacts API v3 Reference
• Request URI: https://www.google.com/m8/feeds/contacts/default/full?q='query'&max-results=1
• HTTP Header GData-Version 3.0