Add "Edit Router" to allow to change router type

Neutron DVR implementation allows to change router type from
centralized to distributed. This commit adds "Edit Router" form
which is not implemented so far to allow this feature.

This commit also adds:
- admin_state field to the router detail.
- documentation on a new option enable_distributed_router

Completes blueprint enhance-horizon-for-dvr
Change-Id: I4b46e44c417726217ed034e305827b102ba656f8
Add a config option to disable Router panel

Neutron setup allows operators not to enable Router feautre
(by not using Router service plugin in neutron.conf) and
some Neutron plugin does not support Router feature.
According to bug 1350639 there is also a case where operators
want to disable Router panel from their policy.
It seems nice we have a option to control Router panel.

This commit add a new option 'enable_router' to OPENSTACK_NEUTRON_NETWORK.
The default is True since router feature is enabled in most deployments
and it is the current default behavior of Horizon.
If this option is False, Router panel will disappear.

blueprint hide-router-panel-by-config
Partial-Bug: #1292022
Closes-Bug: #1350639
Change-Id: If90517bd35c5b18173c54c14a1ba229f97ba4797
Disable Floating IP features if Neutron router is disabled

If the config option 'enable_router' is set to False,
Floating IP features are disabled when Neutron is enabled.
It does not affect when Neutron is disabled.

It also adds unit tests for api.network.servers_update_addresses
which is affected by this change.

Completes blueprint hide-router-panel-by-config
Closes-Bug: #1292022
Change-Id: Ib63c6a0e7bb5661d4a60d10a1722fdad978b50bb
Merge "Add "Edit Router" to allow to change router type"
Merge "Add a config option to disable Router panel"
Merge "Disable Floating IP features if Neutron router is disabled"