Add a new handler for empowering special query

* Adds compatiblity with libsaas 0.4 (master)
* Adds filter and sort to the get method

To fitler and sort in the empowering API the url is like:
`https://api.empowering.cimne.com/v1/contracts/?where="dateStart"<"2013-10-11T16:37:05Z"`
`https://api.empowering.cimne.com/v1/contracts/?sort={"dateStart": -1}`

This change permits use where and sort to the API