Added functionality for cloud server Tags to the 'server create' command

[WalshStephen]

Version:

knife-rackspace-1.0.4

Environment:

OS, cookbook, etc. are irrelevant really for this enhancement request but nonetheless, my workstation is RHEL6

Scenario:

I would like to be able to add server tags that will show under the Tags column, on my RackSpace Cloud portal, when the server is created. Presumably, this could be done with a '-T' tag in the 'knife rackspace server create' command.