[#896] Fix indent bug
[#896] Add project_extra API endpoint

The requirements of Up are easiest to accomodate with a custom endpoint
for projects with some additional data.

This is solved by adding the project_extra endpoint. It provides for
limited filtering as described in a previous commit and also includes
the full data of the location objects associated with the project as well
as some of the data from the partnership objects.
Merge pull request #910 from akvo/feature/896_rest_projects_organisation_filter

Code reviewed