[Frontend] Flex; Tweaks to slider knobs

open #889
- Converted TC elements to use flex
layout instead of abs pos;
- Knob size increased;
- Knob grippies added;

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

@@ -32,8 +32,8 @@ $sliderColorBase: $colorKey;
 $sliderColorRangeHolder: rgba(black, 0.1);
 $sliderColorRange: rgba($sliderColorBase, 0.3);
 $sliderColorRangeHov: rgba($sliderColorBase, 0.5);
-$sliderColorKnob: pushBack($sliderColorBase, 15%);
-$sliderColorKnobHov: $sliderColorBase;
+$sliderColorKnob: $sliderColorBase;
+$sliderColorKnobHov: pullForward($sliderColorKnob, $ltGamma);
 $sliderColorRangeValHovBg: rgba($sliderColorBase, 0.1);
 $sliderColorRangeValHovFg: $colorKeyFg;
 $sliderKnobW: 15px;