Don't set if equal, on edit cylinders and weigth types.

Don't set the cylinders and weight types if they are
the same than before, this fixes a bad thing that happened
when playing with the values. it could blank out the values
carefully chosen by you.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
'Cancel' action Cancels editing Cylinders.

Made the default 'Cancel' action correctly cancel
the cylinder edition. This is needed only because
we bypassed the default behavior on Qt that took
care of this, because we wanted to have more control
on how the view would update the items accordingly
with wich one of the cylinders were selected
on the edition pane - the pressure and size of the
cylinders needed to have it's data set, but the Qt
Model/View system *thinks* that cancel-edition is
simply 'do not commit the edition data, then.' wich
would not work with us, because we passed the strange
data already. So, I created a backup data that serves
us very well. When the user cancels, this backup data
is added back on the cylinder, making everything as
it was before.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>