- restructure rake tasks

  this splits up the concatination and minification into two
  tasks so that we can just build angular.js quickly without wasting
  time with minification which is often not needed when just debugging
  some issue on 3rd party site.

- use symlinks when creating final zip file

- switch from btar to zip

- get rid of version numbers from filenames

- rewrite version numbers in all index files

Closes #1226

Short summary: if you use local node server everything should work as before,
if you use GAE, everything should work now as well, but we pull assets from CDN.

- GAE doesn't support ':' in filenames, so I had to replace it with '_'
  but only in the filename, all servers were reconfigured to rewrite the
  urls from : to _ when doing file lookup
- We now pull angular assets from google CDN when deployed on GAE (locally
  or in production). When running on a non GAE server we pull assets from
  ../ directory as before
- Since only certain versions of Angular are available on CDN and we want
  to be able to autodeploy docs, I had to pin down the Angular files
  to a "stable" version when running on GAE

Create build for other modules as well (ngResource, ngCookies):
- wrap into a function
- add license
- add version

Breaks `$sanitize` service, `ngBindHtml` directive and `linky` filter were moved to the `ngSanitize` module. Apps that depend on any of these will need to load `angular-sanitize.js` and include `ngSanitize` in their dependency list: `var myApp = angular.module('myApp', ['ngSanitize']);`