Bug 830644 - Support WVGA and other non-HiDPI screen dimensions and resolutions
 * homescreen: px to rem, support 5 rows of icons, small tweak in e.me page
 * added @2x assests for homescreen
Merge pull request #8335 from basiclines/responsive-ui

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