Added 3 Routers related testcases for Neutron API

This submission adds four test cases namely
'test_create_show_list_update_delete_router',
'test_add_remove_router_interface_with_port_id'' and
'test_add_remove_router_interface_with_port_id'.
The supporting methods are added to network_client.py file in
'services/json/' directory.
The script covers the actions 'Create/Delete/Update/Update/Show/Add
Interface/Remove Interface' related to Routers.

Change-Id: Ibed53376a2637105f6163519648bb8a668aaf9c7
Implements: blueprint quantum-test-l2-abstraction
Testcase to create bulk networks in one API call

Added "test_bulk_create_delete_network" test case in the
test_networks.py script of "api/networks" tests.
Also added supporting method "create_bulk_network" to
network_client.py.

Change-Id: I8325caf5405714686fa2e78c7c1589854e271860
Implements: blueprint quantum-test-extended-coverage
Merge "Added 3 Routers related testcases for Neutron API"
Merge "Testcase to create bulk networks in one API call"