Bug 830644 - Support WVGA and other non-HiDPI screen dimensions and resolutions

- Added base files to support handling resources for HIDPI devices at make level
- Added default wallpaper @2x version

Not sure how to handle this set of PR, maybe will be fine to keep only Bug 830644 and re-open this same PR each time we need to add new supported applications to do not create hundred of different PR

@rexboy7 @timdream @vingtetun @jmcanterafonseca @arcturus @dcoloma 

r=?