Hide some diff editor controls when diff editor is bound to a file.

Remove unnecessary anymore "ignoreWhitespace" argument
from functions which read a patch file.

Transfer the ownership of reloader into controller.

Task-number: QTCREATORBUG-13250
Change-Id: I68183005b845d6ece9ea2be9888abc8597310426
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>