Fixed and added new functions to Parser class

 - Added warning when trying to interpret unknown sections

 - Changed the exposed functions of the Parser class

The changes to the exposed functions of the Parser class is to ease
the use of the class by third party libraries. The aim is to be able
to write a complete application using this very same class.
Added new default values to the Report properties

Added default values to the lap results properties
Added simple visualizer

Added a simple heart rate data visualizer as a demostration on
how to use the base clases. This class depends on matplotlib
and PySide.