Simplify CLI run-plan command

[ChrisC]

The CLI command to run test plans could be simplified. Some suggestions:

• Remove or simplify the globbing pattern for identifying tests to run (we do still want to be able to run individual plans or tests however)
• Add defaults for driver urls and reference host (since these rarely change)
• Add defaults for working directory

A really simplified command to run a plan could possibly look like:

node /bin/host.js run-plan --test-plan=horizontal-slider --at=voiceover --browser=safari 

I'm wondering if the read-plan command is ever used? If not, perhaps that command can just be removed?

[jugglinmike]

I'm not aware of any use-cases for read-plan, so removing it sounds like a good idea to me!

When it comes to the --test-plan argument, the extra verbosity of a filesystem path may be warranted. It's easier to understand, and it allows folks to use their shell's autocompletion functionality to avoid typos (e.g. typing ar[TAB]/b[TAB]t[TAB]h[TAB] versus horizontal-slider).