[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/_mixins.scss

@@ -322,13 +322,13 @@
 	color: $fg;
 	outline: none;
 	&.error {
-		background: rgba(red, 0.5);
+		background-color: $colorFormFieldErrorBg;
+        color: $colorFormFieldErrorFg;
 	}
 }
 
 @mixin nice-input($bg: $colorInputBg, $fg: $colorInputFg) {
 	@include input-base($bg, $fg);
-	padding: 0 $interiorMarginSm;
 }
 
 @mixin contextArrow() {