Bug 1068986: convert MediaFrame to use background-image instead of <img>

fix failing unit tests

fix the failing python unit tests with a CSS selector change

fix busted share button by restoring public imageblob property on MediaFrame
Bug 1072125 - [Settings] position of label and carrier name are wrong
Bug 1071634 - ICE Contacts Group Shortcut seems to be visually incorrect
Bug 1069791 - Add Firefox OS default theme.