More strict checking & error handling of invalid commands/options

[acburdine]

I've run into a couple of odd issues with denali commands via the CLI, meaning that there likely needs to be more strict checking of commands as well as error reporting.

• the CLI should error when a command doesn't exist. After the split from denali, the denali serve and denali addon commands disappeared. While the issue of adding them back likely belongs in Denali itself, the CLI at the moment doesn't output anything - it says denali-cli <version> [global|local] then denali <version> [global|local] then exits.

• Arguments should be more strictly checked. I tried running denali addon new (before I realized that the denali addon command had been removed), and instead of throwing an error, or even exiting, denali went on to generate a new app with the name new. (So in the end denali addon new = denali new new)

It is possible that these are just bugs instead of things that need to be added, but thought I'd write them down regardless.