Complete refactor of api.py

This patch introduces validation through jsonschema instead of using a
custom format. In order for other API versions to extend this, this
patch implements a base API under transport.api that should be extended
for every API version.

An example of this can be found in test_api.py, future patches will have
more realistic examples and extensions of this class.

The patch also moves api.py under v1/ since Api definitions are version
specific.

Partially-Implements blueprint python-marconiclient-v1

Change-Id: Ie7eacc63deeacb67edfada6ceb5c4956c5adc0b0