[Frontend] Inspector-related fixes

open #244
Fixing scroll issue in Inspector via flex layout;
Added new _archetypes.scss file for .l-flex* and .col styles;
moved .col and associated mixin out of _layout.scss
and into _archetypes;

platform/commonUI/general/res/sass/_main.scss

@@ -21,6 +21,7 @@
  *****************************************************************************/
 @import "effects";
 @import "global";
+@import "archetypes";
 @import "about";
 @import "text";
 @import "icons";