Improve "openstack server xxx" commands to effect on multiple servers.

NOTE: This BP has been redirected to a new one:
https://blueprints.launchpad.net/python-openstackclient/+spec/multi-argument-compute

Improve "openstack server xxx" commands to effect on multiple servers.

Now in Openstack client, some commands are able to be operated on
more than one instances. eg:

# openstack server delete -h
usage: openstack server delete [-h] [--wait] <server> [<server> ...]

Delete server(s)

positional arguments:
  <server> Server(s) to delete (name or ID)

But more commands could only accept one server. eg:

# openstack server pause -h
usage: openstack server pause [-h] <server>

Pause server

positional arguments:
  <server> Server (name or ID)

And also many other commands. So improve these commands to accept multiple servers. A lot of commands are going to be changed in this BP, but not at one time. Will change some of them first, and when the changes are confirmed, go on to the rest of them.

And there are some commands not supported by osc (start and stop). Also implement them.

The commands will be improved as this BP going on:

Step 1: implement unsupported commands (In progress)
---------------------------------------------------------
Todo: reset-state.
Done: start, stop

Step 2: basic operation on servers (In progress)
---------------------------------------------------------
Todo: set/unset, rescue/unrescue, suspend/resume, create, reboot
Done: delete, pause/unpause, lock/unlock

Step 3: migration operations
---------------------------------------------------------
Todo: migrate, resize, rebuild
Done:

Step 4: other operations
---------------------------------------------------------
Todo: add security group, remove security group, add volume, remove volume, image create
Done:

These commands may take one server, but multiple groups/volumes,images.

No need to change:
---------------------------------------------------------
list, show, ssh

This BP will be used to track the progress, and will move items in Todo to Done when the work is finished.

There is another BP adding unit tests for the commands:
https://blueprints.launchpad.net/python-openstackclient/+spec/osc-unit-test-framework-improvement