Move model related code from MainWindow and adjustments.

Moves the DiveTrip model related code to models.h

The DiveTripModel was implemented in three parts:

 DiveTripModel.h
 DiveTripModel.cpp
 MainWindow.cpp (the code to populate the model)

This patch changes the DiveTripModel from it's original
implementation to the file models.h, wich should store
all models (Dirk requested the Qt developers to not create
2 files per class, but instead to use a file for functionality,
and data-models are one functionality.)

Besides that, this code cleans up a bit the style:
removed operator<< for .push_back, const references where they apply,
moved the internal DiveItem class to the .cpp since it should be visible
only to the DiveTripModel class, and redesigned the current interface of
the model to be identical of the GTK one (used the UTF8-star and 2
subscribed, for instance).

Amit (the creator of the original code) should comment here if it's ok
with my changes.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Initial version of the Star Picker Widget.

A very simple to use widget:
StarWidget *stars = new StarWidget( windowParent);
stars->setMaximumStars(10);
stars->setCurrentStars( rand()%10);
stars->show();
connect(stars, SIGNAL(valueChanged(int)), someObj, SLOT(starsChangedValue(int)));

It currently uses a 'star.svg' file on the same folder as the binary.

Signed-off-by: Tomaz Canabrava <tcanabrava@kde.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>