[Frontend] WIP

Fixes #1677
Refactor and re-organize alert and status colors;
Rename _limits.scss to _status.scss;
Style Guide additions in progress;
VERY WIP, NEEDS UNIT TESTING FOR REGRESSION.

platform/commonUI/themes/espresso/res/sass/_mixins.scss

@@ -13,3 +13,10 @@
     // For dark interfaces, darker things move back - opposite for light interfaces
     @return darken($c, $p);
 }
+
+@function bgFg($c) {
+    // Given a single color, return valid background and foreground versions of that color
+    $bg: darken($c, 20%);
+    $fg: lighten($c, 20%);
+    @return $bg, $fg;
+}