Adds up/down aliases for cluster and node start/stop commands.

After using ccm everyday I found this to be annoying enough to fix:

ccm status uses the word 'UP' and 'DOWN' for nodes, but has commands 'start' and 'stop' to actually change that status. The mnemonic for me is broken as I'm always typing up/down instead of start/stop, so I added aliases so that I can use any of the following:

ccm start
ccm stop
ccm up
ccm down
ccm node1 up
ccm node1 down
ccm node1 start
ccm node1 stop

I didn't want this to be too crufty, so I'm hiding these extra up/down commands from the help system and only adding a comment to the description of the original command.