Calendar rebase (3) 

This replaces #1352.
We are sanitizing the hash for security reasons, right?

Not exactly sure what to do so: we sanitize in _handleKeydown like this:
````
this.element.find(
	this._sanitizeSelector( "#" + this.grid.attr( "aria-activedescendant" ) ) 
	+ " > a:first"
).mousedown();
````

and add a cache for elements in _setActiveDescendant and like this 
````
this.activeLinkCache[ id ] = this.grid.find( this._sanitizeSelector( "#" + id ) ).find ( "a" );
...
````
We would need to empty and rebuild that cache on every refresh as the grid items are rebuilt.