Address large font size edge cases

Fix some visual bugs occuring at large font size:
  * Contact names break onto the next line after their avatars in
    message detail screen
  * Settings menu font-size failed to scale
  * Handle Content overflow in modals.

// FREEBIE

background.html

@@ -10,7 +10,7 @@
               <div class='global-menu menu'>
                 <button class='hamburger' alt='signal menu'></button>
                 <ul class='menu-list'>
-                    <li class='settings'>{{ settings }}</li>
+                    <li class='showSettings'>{{ settings }}</li>
                     <li class='show-debug-log'>{{ submitDebugLog }}</li>
                     <li class='restart-signal'>{{ restartSignal }}</li>
                 </ul>