Improve Blockly controls

Fixed Issue #1352:

1. Cursor changes to pointer when hovering over the backpack and zoom elements on the right side of screen.
2. Zoom elements and trashcan are now black to increase their visibility on the screen, especially when the grey sidebar is extended over them.
3. Shifted the positioning of the zoom control images from the sprites.png image so that no more ugly lines display around the controls.

appinventor/blocklyeditor/media/ai2blockly.css

@@ -28,3 +28,11 @@
   fill: #ddd;
   fill-opacity: .8;
 }
+
+.blocklybackpackImage:hover {
+  cursor: pointer;
+}
+
+.blocklyZoomButton:hover {
+  cursor: pointer;
+}

appinventor/blocklyeditor/src/backpack.js

@@ -205,6 +205,9 @@ Blockly.Backpack.prototype.createDom = function(opt_workspace) {
       this.svgGroup_);
   this.svgBody_.setAttributeNS('http://www.w3.org/1999/xlink', 'xlink:href',
       Blockly.pathToBlockly + this.BPACK_CLOSED_);
+
+  this.svgBody_.setAttribute('class', 'blocklybackpackImage');
+
   return this.svgGroup_;
 };
 

blockly @ c5ead64c

-Subproject commit 44ad45698c4625844629696be94dcc60ca691f48
+Subproject commit c5ead64c2b930e0794031ea999df9dca62bcf0e1