[Frontend] Styling for controls

Fixes #1324
CSS, markup, WIP adding reset button

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

@@ -50,6 +50,7 @@ $sliderKnobW: 15px;
 $sliderKnobR: 2px;
 $timeControllerToiLineColor: #00c2ff;
 $timeControllerToiLineColorHov: #fff;
+$colorTransLucBg: #666; // Used as a visual blocking element over variable backgrounds, like imagery
 
 // General Colors
 $colorAlt1: #ffc700;