Adding more ember admin tests

- improving the implementation of thenOpenAndWaitForPageLoad
- adding a class into the settings templates to more easily test which pane we are on
- adding more, and updating more of the settings tests
- added the editor tests

ghost/admin/templates/settings/apps.hbs

@@ -3,7 +3,7 @@
     <h2 class="title">Apps</h2>
 </header>
 
-<section class="content fade-in">
+<section class="content settings-apps fade-in">
     <table class="js-apps">
         <thead>
             <th>App name</th>

ghost/admin/templates/settings/general.hbs

@@ -6,7 +6,7 @@
     </section>
 </header>
 
-<section class="content fade-in">
+<section class="content settings-general fade-in">
     <form id="settings-general" novalidate="novalidate">
         <fieldset>
 

ghost/admin/templates/settings/user.hbs

@@ -6,7 +6,7 @@
     </section>
 </header>
 
-<section class="content no-padding fade-in">
+<section class="content settings-user no-padding fade-in">
 
     <header class="user-profile-header">
         <img id="user-cover" class="cover-image" {{bind-attr src=cover title=coverTitle}} />