Bug 876765 - Part 1: Factor out search view into SearchEngineRow. r=lucasr

--HG--
rename : mobile/android/base/resources/layout/awesomebar_suggestion_row.xml => mobile/android/base/resources/layout/search_engine_row.xml
rename : mobile/android/base/resources/layout/awesomebar_suggestion_item.xml => mobile/android/base/resources/layout/suggestion_item.xml
Bug 876765 - Part 2: Give buttons a focusable state in AwesomeScreen. r=lucasr
Bug 876765 - Part 3: Enable navigating to search suggestions with gamepad. r=lucasr
Bug 876765 - Part 4: Fix search suggestion opt-in prompt focus behavior. r=lucsar