Create an array from the options instead of a hash.

This allows for an option to be entered multiple times on the command line.
example: "rhn-channel -a --channel=1234 --channel=5678"
Add register command with proxy and satellite options and tests.
Add proxy support to subscribe, refactor proxy details into a method.

Make register and subscribe options required.
Allow for multiple pools to be specified.
Improved test coverage of common