QtIFW

Replace all occurrences of "can not" with "cannot"

Also fix some other issues in the touched strings,
making them comply to Qt style.

Change-Id: I46515e1a3bec5e21610943ded2ef7fa1f09a4a15
Reviewed-by: Kai Koehne <kai.koehne@theqtcompany.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>