made the "trashzone" configurable through the "removableOptions". All the jq...

made the "trashzone" configurable through the "removableOptions". All the jq ui options should be supported now
added an "inTrashZone" flag to fix a problem when there is an overlapping between the grid and the "trashzone"

PS I'm not very experienced in github / jq plugins, hope I didn't break anything... if accepted the information about "removableOptions" parameter should be added to the readme doc

src/gridstack.jQueryUI.js

@@ -77,13 +77,7 @@
 
     JQueryUIGridStackDragDropPlugin.prototype.droppable = function(el, opts) {
         el = $(el);
-        if (opts === 'disable' || opts === 'enable') {
-            el.droppable(opts);
-        } else {
-            el.droppable({
-                accept: opts.accept
-            });
-        }
+        el.droppable(opts);
         return this;
     };
 

src/gridstack.js

@@ -603,6 +603,9 @@
             disableResize: opts.disableResize || false,
             rtl: 'auto',
             removable: false,
+            removableOptions: _.defaults(opts.removableOptions || {}, {
+                accept: '.' + opts.itemClass
+            }),
             removeTimeout: 2000,
             verticalMarginUnit: 'px',
             cellHeightUnit: 'px',
@@ -750,9 +753,7 @@
         if (!self.opts.staticGrid && typeof self.opts.removable === 'string') {
             var trashZone = $(self.opts.removable);
             if (!this.dd.isDroppable(trashZone)) {
-                this.dd.droppable(trashZone, {
-                    accept: '.' + self.opts.itemClass
-                });
+                this.dd.droppable(trashZone, self.opts.removableOptions);
             }
             this.dd
                 .on(trashZone, 'dropover', function(event, ui) {
@@ -761,6 +762,7 @@
                     if (node._grid !== self) {
                         return;
                     }
+                    el.data('inTrashZone', true);
                     self._setupRemovingTimeout(el);
                 })
                 .on(trashZone, 'dropout', function(event, ui) {
@@ -769,6 +771,7 @@
                     if (node._grid !== self) {
                         return;
                     }
+                    el.data('inTrashZone', false);
                     self._clearRemovingTimeout(el);
                 });
         }
@@ -1071,7 +1074,7 @@
             }
 
             if (event.type == 'drag') {
-                if (x < 0 || x >= self.grid.width || y < 0 || (!self.grid.float && y > self.grid.getGridHeight())) {
+                if (el.data('inTrashZone') || x < 0 || x >= self.grid.width || y < 0 || (!self.grid.float && y > self.grid.getGridHeight())) {
                     if (!node._temporaryRemoved) {
                         if (self.opts.removable === true) {
                             self._setupRemovingTimeout(el);