remove slotCurrentPageChanged and call it directly

 - also renamed it to better name: executeControlScript

Change-Id: Id2bb7cada2386561c2b25b158c6aa101382e5cc4
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>
Fix possible crash. Disable close button during installer run.

Change-Id: I6a0affab7394e3ae9669904bbfc48617b5cb1bd5
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>