[Frontend] Mods in progress to form layout

open #638
Major progress on form-row markup and CSS when
in Inspector 'part' context; General fixes cleanups
to custom checkbox/radio CSS;

platform/commonUI/general/res/templates/object-inspector.html

@@ -36,7 +36,7 @@
             <mct-splitter class="splitter-inspect-panel mobile-hide"></mct-splitter>
             <div class="split-pane-component pane bottom">
                 <div class="abs holder holder-elements l-flex-col">
-                    <em class="flex-elem">Elements</em>
+                    <em class="flex-elem t-inspector-part-header">Elements</em>
                     <mct-representation
                             key="'edit-elements'"
                             mct-object="domainObject"