Augment postman neutron collection and added RouterHandler skeleton.

Added more crud operations to postman neutron collection: router.
Added RouterHandler (which will be needed for L3 forwarding feature).

Change-Id: Ifafb3b4892772f1704d2dd2479c0c2a77db36c67
Signed-off-by: Flavio Fernandes <ffernand@redhat.com>