Visually align headings inside grid rows

When the first heading on the page is inside a grid row, it doesn’t
vertically align properly with the navigation. This is because it
isn’t targeted by the selector that does this for pages without
an initial grid row.

This commit:
- adds an extra selector to target these headings
- makes the ‘add new thing’ buttons maintain their alignment with
  the page heading

app/assets/stylesheets/_grids.scss

@@ -26,7 +26,7 @@
 .align-with-heading {
   display: block;
   text-align: center;
-  margin-top: 45px;
+  margin-top: 35px;
   padding-left: 2px;
   padding-right: 2px;
 }

app/assets/stylesheets/app.scss

@@ -60,6 +60,14 @@ a {
     margin-top: $gutter;
   }
 
+  > .grid-row  {
+    
+    .heading-large {
+      margin-top: $gutter;
+    }
+    
+  }
+
 }
 
 .highlight {