[Frontend] Convert main left pane elements to flex layout

open #250
Markup mods in browse.html;
Renamed .holder-create-and-search to
.holder-treeview-elements;
TO-DO: fix search results to scroll properly;

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

@@ -108,7 +108,12 @@
 }
 
 .l-flex-row { @include flex-direction(row); }
-.l-flex-col { @include flex-direction(column); }
+.l-flex-col {
+    @include flex-direction(column);
+    .flex-elem {
+        margin-bottom: $interiorMargin;
+    }
+}
 
 .l-flex {
     @extend .l-flex-row;

platform/commonUI/general/res/sass/mobile/_layout.scss

@@ -42,7 +42,7 @@
         }
     }
 
-    .holder.holder-create-and-search {
+    .holder.holder-treeview-elements {
         right: $bodyMargin !important;
     }
 

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

@@ -180,7 +180,6 @@
         text-transform: uppercase;
         height: $ueTopBarH;
         line-height: $ueTopBarH;
-        margin-bottom: $interiorMargin;
     }
 
     .primary-pane {
@@ -198,7 +197,7 @@
         //        bottom: $interiorMargin;
         //    }
         //}
-        .holder-create-and-search{
+        .holder-treeview-elements{
 
         }
         .search-holder {
@@ -293,7 +292,7 @@
     }*/
 
     // Specific elements margins
-    .holder.holder-create-and-search {
+    .holder.holder-treeview-elements {
         top: $bodyMargin;
         right: 0;
         bottom: $bodyMargin;
@@ -373,7 +372,7 @@
     //.pane.left.treeview,
     .tree-holder,
     .splitter-treeview,
-    .holder-create-and-search {
+    .holder-treeview-elements {
         opacity: 0;
     }
 }
@@ -387,7 +386,7 @@
         opacity: 1;
     }
 
-    .holder-create-and-search {
+    .holder-treeview-elements {
         @include trans-prop-nice(opacity, $dur: 250ms, $delay: 200ms);
     }
 }