[#589] Add data to project_update_extra API resource

Refactor "project" field to include the full primary_location as well as
the resource_uri.

Refactor "user" field, separate "full_name" into "first_name" and
"last_name".

Refactor "organisation" field to include the full primary_location.

Add photo to fields that can be filtered on.
Merge pull request #591 from akvo/feature/589_more_project_update_extra

[#589] Code looks good
Merge pull request #598 from akvo/develop

Merge [#589] for 2.3.7 release