fix(dragCursor): don't default the drag cursor to move

BREAKING CHANGE: The drag cursor will no longer be set to `move` by default, to restore the
behaviour set `dragCursor="move"` or use CSS on the draggable elements to change the cursor

Author: mattlewis92

demo/demo.component.ts

@@ -27,6 +27,7 @@ import { Component } from '@angular/core';
         z-index: 2;
         float: left;
         margin-right: 10px;
+        cursor: move;
       }
       [mwlDroppable] {
         background-color: green;

src/draggable.directive.ts

@@ -58,8 +58,6 @@ export interface PointerEvent {
   event: MouseEvent | TouchEvent;
 }
 
-const MOVE_CURSOR: string = 'move';
-
 @Directive({
   selector: '[mwlDraggable]'
 })
@@ -97,7 +95,7 @@ export class DraggableDirective implements OnInit, OnChanges, OnDestroy {
   /**
    * The cursor to use when dragging the element
    */
-  @Input() dragCursor = MOVE_CURSOR;
+  @Input() dragCursor: string = '';
 
   /**
    * The css class to apply when the element is being dragged