Fix EZP-22276: URI templates in Root resource should use query expansion format

> https://jira.ez.no/browse/EZP-22276

Updated REST spec according to [URI template RFC](http://tools.ietf.org/html/rfc6570#section-3.2.8)
EZP-23653: shortened path to API tests fixtures
Merge pull request #1094 from ezsystems/EZP-23653-api_test_fixtures_path

EZP-23653: shortened path to API tests fixtures