[MIE-1608] Added a simple pagination service and implemented it in every endpoint returning lists. 

Pagination Service receives a query object, like: {'offset': 1, 'limit': 50} and a list of items, and return a subset of that list representing the requested page. Default is set to  {'offset': 1, 'limit': 50}

Implemented Pagination Service in every endpoint returning lists. Example: if you go to */api/v1/object/db_user/1/activities* , you can add the query **?limit=20&offset=1** to the URL to filter your results.

Unit tests and bateries provided!
For pagination, I think `offset` is normally an item count, whereas `page` is the page you request. For example, Django's Tastypie implements `offset` the way I described. If we want to support requesting pages, then I think we should accept a parameter `page` that either overrides or can be overridden by `offset`.