[Frontend] Layout and positioning fixes for TC controls

open #889
IN PROGRESS
- Smaller font used on range value;
- More space allocated to left and right
for slider range values;
- Style tweaks to slider look;
- Layout and style of datetime inputs
fixed;
- Input error colors fixed, moved to
theme constants;

platform/commonUI/general/res/sass/controls/_controls.scss

@@ -29,7 +29,7 @@
     .accordion-head {
         $op: 0.2;
         border-radius: $basicCr * 0.75;
-        box-sizing: "border-box";
+        box-sizing: border-box;
         background: rgba($colorBodyFg, $op);
         cursor: pointer;
         font-size: 0.75em;