Implementing simple operator API

Setup executable to use wsgiref.simple_server
Simple setup of pecan
Defined controllers that define the API resources
Implemented all controllers to manipulate database and send to handler
Added repository methods required for creating multiple items in one transaction
Defined a few API exceptions based of wsme exceptions
Defined the wsme types that define the resource response and request bodies
Defined an abstract handler that all handlers should subclass
Defined a simple handler that is responsible for sending to controller
Added some wsme type tests

Implements: bp/operator-api

Change-Id: I0d91934db47a6e45f0c9ac22089f8689957bd239