Moved the plot from the cairo version to the Qt version

Started working on the Qt version of the Plot, initially
nothing is printed - but this is not a bad thing,
the program doesn't explodes too. :)

some work had to be done about the 'bool/gboolean' stuff
so I removed all gbooleans in the code that I'v encountered.

A new file was created ( profile.h ) so I could put the
signatures of helper methods that cairo used to call.

till now the code computes the max limits.
Next patch the first drawing will be made.

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