Added support for Completing on the Cylinder Type delegate

I had to immprove the TankInfoModel with two new methods,
insertRows and setData, because the delegate used this
model to show what kind of Tanks we are offering.
Since the user can enter a new type of Tank, it's important
to add this tank to all lists using the delegates.

I Also added two new methods on the delegate itself,
to correctly shows the data, and set the data on the
model. This also will help dirk with a working example
on how to edit things while using a delegate.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Also changes the size and working pressure of the cylinders

this is more a 'Well, this is how we do it' than an actuall
good commit. I'm probably using the wrong conversion paradigm
( none ) to convert the data from psi / bar and such, it
changes the model with wrong data.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Allow the CylindersModel delegate to pass data in without unit conversions

With this we should have tank editing mostly done.

See #122

(it's not quite fixed, we need the equivalent code for weight systems)

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>