Bug 873251 - [Metro] Update buttons and backgrounds of Firefox app bar. r=jwilde

--HG--
rename : browser/metro/theme/images/forward.png => browser/metro/theme/images/appbar-forward.png
rename : browser/metro/theme/images/reload.png => browser/metro/theme/images/appbar-reload.png
rename : browser/metro/theme/images/stop-hdpi.png => browser/metro/theme/images/appbar-stop.png
Bug 811392 - Work - Choose better background colors for location text in the Firefox app bar. r=fryn
Back out 2d970c9c1fad - Bug 882858 Because of mochitest-browser failures in browser_CTP_drag_drop.js and perhaps browser_pluginnotification.js