Added support for showing the Stars on the DiveTable

For the stars on the dive table I had to rework a bit my
StarRating widget, because it used a pixmap for each widget
that were created. Not it uses only 2 pixmaps: the active
and inactive ones.

A new file was created named modeldelegates(h, cpp) that
should hold all delegates of the models. For the GTK / C
folks, a 'Delegate' ia s way to bypass the default behavior
of the view that's displaying the data.

I also added the code to display the stars if no delegate
is set ( good for debugging. )

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Add support for remembering settings

Use QSettings to provide persistent storage of settings. For example, we
store and restore the size of the MainWindow.

We use the organisation name hohndel.org and keep subsurface as the
application name.

A section is specified for things to do with the MainWindow; other
sections could be added e.g. for preferred units?

Signed-off-by: Amit Chaudhuri <amit.k.chaudhuri@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Minor coding style cleanups - and use core logic function

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Merge branch 'RenderStarsOnTable' of https://github.com/tcanabrava/subsurface into Qt