[Frontend] Mods to layout element drag handles and editing behavior

WTD-951
layout.html:
Added classes to and removed inline styles from drag handles,
Removed edge handles, leaving corner handles in NW, SW and SE only;
Added hover classes to display corner handles while editing;
Modified z-indexing to allow view switcher to be accessed while editing;

platform/commonUI/general/res/sass/user-environ/_frame.scss

@@ -54,6 +54,7 @@
 		.view-switcher {
 			//display: none;
 			opacity: 0;
+			z-index: 10;
 		}
 		&:hover .view-switcher {
 			// Show the view switcher on frame hover