updates for docs, including selectable/droppable

selection/unselect_callback.txt

@@ -0,0 +1,24 @@
+
+unselect *1.4.6*
+================
+
+A callback that will fire when the current selection is cleared.
+
+<div class='spec' markdown='1'>
+function( *view*, *jsEvent* )
+</div>
+
+A selection might be cleared for a number of reasons:
+
+1. The user clicks away from the current selection (doesn't happen when [unselectAuto]() is `false`).
+
+2. The user makes a *new* selection. The `unselect` callback will be fired before the new selection occurs.
+
+3. The user moves forward or backward in the current view, or switches to a new view.
+
+4. The [unselect](unselect_method) method is called through the API.
+
+
+`jsEvent` holds the primitive JavaScript event with information such as mouse coordinates.
+If `unselect` has been triggered via the [unselect method](unselect_method), `jsEvent` will be `undefined`.
+(added in version 1.4.7)