Minify and concatenate client js's

Implements https://github.com/jquery/download.jqueryui.com/issues/67

Minification gains:
- download: 17% (314.6KB -> 261.7KB);
- themeroller: 15% (305.2KB -> 259.8KB);

Highlights:
1. Grunt default task now (a) jshint, (b) handlebars, which updates frontend templates, (c) uglify.
1. On development, download or themeroller index still loads each .js individually, better for development. On production, it uses the minified bundle.

Note:
1. lzma lib is very significant, its size is 100KB (minified);

Remaining TODO:
1. Use minified jquery.js;