[bug 1003288] Add user-agent to FxOS form

Author: willkg

fjord/feedback/static/js/mobile/fxos_feedback.js

@@ -154,7 +154,8 @@
                 'platform': 'Firefox OS',
                 'locale': $('#locale').val(),
                 'country': $('#country select').val(),
-                'device': $('#device select').val()
+                'device': $('#device select').val(),
+                'user_agent': navigator.userAgent
             };
 
             version = inferFxosVersion();