XD-1328 Modularize UI (Part 1)

- Add RequireJS support for the main app
  - Add RequireJS configuration for xdAdmin app
  - Define AMD modules
  - Bootstrap app with these modules
  - Disable minification of js files for now
- Update/modify grunt tasks
  - Change yeoman.app -> xd.app
  - Remove unused grunt tasks
  - Modify bower components targetDir to use lib/
  - Remove bower components that are not used
  - Adde more comments and fixe some of the grunt build tasks
- Modularize controllers

TBD:

 - Support minification of JS files with requireJS optimizer
 - Fix karma unit tests and add requireJS support
 - Modularize controllers and services further to define
   individual AMD modules for each controller/service.

Jira: https://jira.spring.io/browse/XD-1328