[bug 913629] Fix south migration history.
Merge pull request #604 from glogiotatidis/fix-south-2

[bug 913629] Fix south migration history.
[fix bug 911980][fix bug 848256][fix bug 848257] API refactoring, tests and bug fixing.

* Refactor API to not use the ElasticSearch backend (bug 911980)
* Explicitly set the fields returned by UserResource
* Fix filters containing spaces (bug 848257)
* Fix filters with commas (bug 848256)
* Fix default data ordering (bug 914384)
[fix bug 862058] Export username in UserResource.
[bug 908702] City and Country API Endpoints.
[bug 908702] Groups, Skills and Languages API Endpoints.
Merge pull request #601 from Sancus/multiaccounts

[Fix Bug 881852] add multi-account field to user profile
Merge pull request #599 from glogiotatidis/new-api

API