Uni requesthandler

Replace GetRequestHandler and PostRequestHandler with one class AllRequestHandler that handles all verbs - Get and Post work as before; AllRequestHandler should behave exactly the same as the code it replaces for Get and Post requests,  Put and Delete are handled but correctness is not tested on these verbs. 

This will also lead to a lot of internal simplification that is not included in this pull request.
(this passes all relevant tests)