fix misspelled 'project' in router-create help text

Change-Id: I4874563c0dd7ca35ef153cf24b99e357c0c076b9

Refactored the 'os security group delete' command to use the SDK
when neutron is enabled, but continue to use the nova client when
nova network is enabled.

This patch set introduces a new NetworkAndComputeCommand class
to be used for commands that must support neutron and nova network.
The new class allows both the parser and actions to be unique.
The current DeleteSecurityGroup class is now a subclass of this
new class and has moved under the network v2 commands.

This patch set also introduces a new FakeSecurityGroup class for
testing security groups.

And finally, this patch set updates the command documentation
for security group and security group rule to indicate that
Network v2 is also used.

Change-Id: Ic21376b86b40cc6d97f360f3760ba5beed154537
Partial-Bug: #1519511
Related-to: blueprint neutron-client

Add "os port show" command.

Change-Id: Id87c81640e74c60ae8f247c722c64fdadff022a2
Partial-Bug: #1519909
Partially-Implements: blueprint neutron-client

get_body() is needed in each network files to construct a dict
to pass to sdk proxy. And it is also used by several functions
in each file. So define it as a file level private helper function.

The unified prototype should be:

    def _get_attrs(client_manager, parsed_args):

1. The name, in sdk, the parameter passed to proxy is named "attrs".
   And it is a private method. So let's call it _get_attrs().
2. The parameters, besides parsed_args, when we deal with project
   and project_domain, we have to make use of identity_client. So
   let's pass in the client manager.

Change-Id: Ib044ebd4ddedbcd805f46334a7fe99e4ebb5b249

Follow-up patch of https://review.openstack.org/#/c/269613/
network/v2/subnet and port still use cliff classes directly.
This patch fixes it.

Change-Id: If9d90e5151ece7f4cf1e0d6fd2f32919865f2f2e