Convert course home page to Bootstrap

LEARNER-1694

Fix a11y failure

Fix header styling

Fix layout issues

Further layout fixes

common/static/sass/edx-pattern-library-shims/_buttons.scss

@@ -86,9 +86,9 @@
 }
 
 // ----------------------------
-// #BRAND
+// #PRIMARY
 // ----------------------------
-.btn-brand {
+.btn-primary {
   @extend %btn-shims;
 
   border-color: $btn-brand-border-color;
@@ -150,3 +150,10 @@
     color: $btn-upgrade-color;
   }
 }
+
+// ----------------------------
+// #BRAND
+// ----------------------------
+.btn-brand {
+  @extend .btn-primary;
+}