[Frontend] Apply flex layout to object header elements

open #250
open #260
vista#132
Major refactoring to markup and CSS to apply
flex layout strategy to object headers;
Flex necessary to fix 'overflow: hidden' setting
applied in open90 to object-browse-bar that
was preventing the view switcher menu from
appearing;
Browse, edit, mobile, frames in layouts, etc. all
visually checked in a first go round;
Mobile classes tweaked to fix left and right
margin problems resulting from open90 changes;
z-indexing of Inspector pane and splitters changed
to allow primary pane elements to overflow beneath
when primary pane width is severely constrained;

platform/commonUI/general/res/sass/helpers/_splitter.scss

@@ -29,7 +29,7 @@
     //@include test(red);
     display: block;
     position: absolute;
-    z-index: 1;
+    z-index: 3;
     &:after {
         // The handle
         content:"";