ReqMgr2 request injection prototype

-created new package DataStucts containing Request, RequestTypes and
    RequestStatus definition
-DataStructs/Request contains validation of input request arguments
-Service/Request.post - request injection method - entire ReqMgr1 injection
    flow is now covered, though a number of request arguments manipulations is
    not entirely figured out, but majority is.
    Spec instantiation and Couch storing finished.
-Service/Request.delete method implemented.
-reqmgr2.py client script able to create, delete, query requets in ReqMgr2.

@ticoann please review. basically each TODO designated block is a smaller or
larger topic for discussion.
Merge pull request #4701 from zdenekmaxa/reqmgr2-request-injection

ReqMgr2 request injection prototype