VPNaaS Cisco REST client enhance CSR create

For the create of the REST client object that represents a Cisco CSR,
all of the info needed were passed in as separate parameters. This
change just uses a dict instead, so that additional parameters can
be added w/o changing the API.

Updated the currently unused UT module, just so that it can be used
locally and stays up-to-date until it can be converted to use the
new requests-mock package.

Change-Id: I5d4f439cc7ffe125cea9ed3407b70645587a739a
Closes-Bug: 1336478
Add L3 Extension for Distributed Routers

This patch introduces the model and extension
framework for implementing distributed virtual
routing on top of Open vSwitch.

A new admin-only 'distributed' (as opposed to a
'centralized' or legacy-mode) attribute is added
to the API router resource. It is possible to convert
an existing (centralized) router to a distributed
one; the opposite conversion, even though allowed by
the API, may not be honored by the underlying
plugin implementation and an appropriate error will
be reported.

When creating a router (regardless of the user role),
Neutron will rely on a system wide configuration, whose
default currently allows to create 'centralized' routers.

Tests are added for basic unit coverage; when the first
building blocks for neutron-testing-refactor
are complete, functional testing will be added.
This is because we should be moving away from how
extension tests have been done up until now.

Partially-implements: blueprint neutron-ovs-dvr

DocImpact

Change-Id: I7227fbe2718eba6665a5afb5dcaaaa77b341091f
Authored-by:    Swaminathan Vasudevan <swaminathan.vasudevan@hp.com>
Co-Authored-By: Armando Migliaccio <armamig@gmail.com>
Merge "Add L3 Extension for Distributed Routers"