Two RTL Fixups in Studio and CAPA problems

- Fixed RTL icon margin in the studio
  - Make math equation fields always LTR in CAPA problems

cms/static/sass/elements/_controls.scss

@@ -193,9 +193,9 @@
 .button {
 
   .icon {
+    @include margin-right($baseline/4);
     display: inline-block;
     vertical-align: middle;
-    margin-right: ($baseline/4);
   }
 }
 
@@ -321,9 +321,9 @@
 
   .ui-toggle-expansion {
     @include transition(all $tmg-f2 ease-in-out 0s);
+    @include margin-right($baseline/4);
     @extend %t-action1;
     display: inline-block;
-    margin-right: ($baseline/4);
     color: $gray-l3;
     vertical-align: middle;
   }

common/lib/xmodule/xmodule/css/capa/display.scss

@@ -141,6 +141,10 @@ div.problem {
     }
   }
 
+  input.math {
+    direction: ltr; // Equations are always English
+  }
+
   .inline {
     display: inline;