[TV] Experimental IAC between system and homescreen
* extract dom rendering from app_list.js to homescreen.js
Merge pull request #2 from dwi2/TV_arch1

[TV] Experimental IAC between system and homescreen
* rename app_list.js to applications.js
* modularize appList's view (separated from homescreen.js)
* don't use '?' to refresh the url in homescreenWindow
1. create hs_layout_editor which is a grid based layout engine
2. create widget editor which uses hs_layout_editor and shows a sample view of it.
3. relayout the html