feat(gen) add grunt-ngdoc

Add jsdoc to generated text and add grunt-ngdocs generated documentation
to /docs.

Add grunt-ngdocs to package.json & Gruntfile.js. Basic support in js templates.
Watch for changes in js files & autoreload docs after regeneration.

Init work at #550

Example:
![documentation](https://f.cloud.github.com/assets/1024920/1951046/570c8952-8169-11e3-98ce-7ad69831924c.png)