kendo.destroy destroys multiple widget instances

Fix telerik/kendo-ui-core#19

Squashed commit of the following:

commit b567b7a6e03f9a667320cf66ac31a2aa7c6660e0
Author: Atanas Korchev <akorchev@gmail.com>
Date:   Tue Apr 22 14:25:39 2014 +0300

    Remove redundant destroy calls.

commit 01e457eab44ccc73ccf9e957dd7930b6ef9d488f
Author: Petyo Ivanov <underlog@gmail.com>
Date:   Tue Apr 22 12:00:47 2014 +0300

    Fix failing remote view reloading test

commit 22c93abf7235c26ab21e14e52869fb95e4ae7971
Author: Atanas Korchev <akorchev@gmail.com>
Date:   Tue Apr 22 11:23:59 2014 +0300

    Destroy all Kendo widgets attached to an element.