Tech: removed jquery-ui and jquiery-ui-angular-drag-drop, replaced with native drag drop for angular, saved ~50kb in js libs, much cleaner & simpler usage, Also changed some behavior for drag drop, now panels are replaced when droped on (switch places), Closes #920

src/css/less/overrides.less

@@ -231,10 +231,6 @@ form input.ng-invalid {
   z-index: 9999;
 }
 
-.dragInProgress .panel-container {
-  border: 3px solid rgba(100,100,100,0.50);
-}
-
 .link {
   color: @linkColor;
   cursor: pointer;

src/css/less/panel.less

@@ -2,6 +2,7 @@
   display: inline-block;
   float: left;
   vertical-align: top;
+  position: relative;
 }
 
 .panel-container {
@@ -98,3 +99,16 @@
 .panel-highlight  {
   .box-shadow(~"inset 0 1px 1px rgba(0,0,0,.075), 0 0 5px rgba(82,168,236, 0.8)");
 }
+
+.on-drag-hover {
+  .panel-container {
+    .box-shadow(~"inset 0 1px 1px rgba(0,0,0,.075), 0 0 5px rgba(82,168,236, 0.8)");
+  }
+}
+
+.panel-drop-zone {
+  display: none;
+  .panel-container {
+    border: 1px solid @grayDark;
+  }
+}