alloy with no arguments, and help, should be more helpful

[kwhinnery]

There's currently no help displayed if the alloy command is run with no arguments. If alloy is run with no arguments, a list of commands should be shown. --help or similar should have the same effect. Running alloy <command> help or similar should display detailed usage information about the command. I think Tony's working this already but want to make sure to prioritize.