Implement CLI method(s): StarterKits #16

braindump, intended to start discussion. nothing here is prescriptive.

At any time, a user should be able to ask the PL CLI what starterkits are available for download.

Current exposed command on editions:

• https://github.com/pattern-lab/patternlab-node/blob/dev/core/lib/patternlab.js#L528-L530
• https://github.com/pattern-lab/edition-node-gulp/blob/master/gulpfile.js#L115-L118

Proposed CLI command:
patternlab starterkit --install

With no additional parameters, perhaps it suggest like https://github.com/pattern-lab/patternlab-node-cli/blob/master/bin/init.js#L236

Proposed option:
patternlab starterkit --install --starterkit-mustache-demo

With this option, it reaches out to install from npm if needed, and then installs similar to

• https://github.com/pattern-lab/patternlab-node/blob/dev/core/lib/patternlab.js#L531-L533
• https://github.com/pattern-lab/edition-node-gulp/blob/master/gulpfile.js#L120-L123