Implement double Esc key press shortcut for canceling continued transform mode

Now if you start a continued transform mode in the transform tool,
you have two options:

1) Press Esc key once to reset the transformation to non-transformed
   state

2) Press Esc key twice to cancel changing the continued transformation

CC:kimageshop@kde.org
BUG:361852
(cherry picked from commit 59ffe8bf10c618e35632b466a34578fee79ca78b)