Add sorting for Collections table

[MaciejWiczk]

Similar to #132, soting collection table would be nice addition to UI.Since Collection Table is paged, this one has to be done on API. Two parameters to be added to endpoint:

• sort_by with field used for ordering
• desc or descending for orderind direction

[pbylicki]

@MaciejWiczk I think this one should be done in a generic way that could be used for collections and keywords and potentially new resources in the API. I would do it like in Django Rest Framework, with url parameter order=-field where optional minus would indicate descending order. We could even allow multiple parameters provided with order=field1&order=field2

[MaciejWiczk]

I didn't know DRF was working that way. I agree with that approach fully.