Yet another iteration on the user interface

* Automatically display the overlay when the card details is opened
  (previously we waited for the mouse to enter the card details panel)
* Improve the design of the minicards badges
* Change the minicard background when it is hovered or selected
* Removes unimplemented features links from the UI
* Fix the board canvas position when the sidebar is open (was hidden
  behind)

Fixes #215

client/components/sidebar/sidebar.js

@@ -102,6 +102,10 @@ BlazeComponent.extendComponent({
   }
 }).register('sidebar');
 
+Blaze.registerHelper('Sidebar', function() {
+  return Sidebar;
+});
+
 EscapeActions.register('sidebarView',
   function() { Sidebar.setView(defaultView); },
   function() { return Sidebar && Sidebar.getView() !== defaultView; }

client/components/sidebar/sidebar.styl

@@ -34,7 +34,7 @@
       display: flex
       flex-direction: column
 
-      li a
+      li > a
         display: flex
         height: 30px
         margin: 0