UP-4295: Added skin architecture; added icon-only app launcher portlet styles

### Skin Architecture Laid Down

* skin.xml and skin-shared.xml pages added with Bootstrap, FontAwesome, jQuery and jQuery UI libraries from the resource server;
* Plain and aggregate compilation of JavaScript and CSS;
* Added Maven LESS compilation to build process;
* Created LESS architecture for further growth:
  - LESS folder can contain directories that pertain to each portlet, with it's own LESS structure;
  - Each portlet should have a parent LESS file that imports the LESS structure;
  - Import the portlet.less file to the jasig-widget-portlets.less for compilation;
  - CSS will be included in the webapp/css folder for style rendering;
* App Launcher portlet has two views now:
  - Icon and Text View: Includes longer container with icon and portlet title and description;
  - Icon Only View: Only shows the portlet icon - on hover, will show the portlet title and description;