Rework shutit command line, turn create skeleton into python

For the reworking of the command line, it should hopefully all be backwards compatible.
Shutit now works with 'subcommands' (like cvs and git). In order to preserve backwards compatibility, I've added some hacks to make it assume that the action is build if it's not been specified.
You can see how it works now with ./shutit --help, then ./shutit build --help or ./shutit skeleton --help

For the conversion of create skeleton to python, I've done some checks with meld and it all seems to agree with the original script.
One thing I couldn't figure out in the original script were the appearances of `$(basename $MODULE_NAME)` - this would strip anything before the final slash of $MODULE_NAME...but the script would blow up if module_name ever had slashes in it in the first place.

Now I can get back to more interesting things.