Remove include path in doxyfile

The include path is useless with MACRO_EXPANSION set to 'NO'
Update styling bat file and format all files with astyle
Improve grammar in Doxygen comments
Use 'class' keyword instead of 'struct' for shape abstract class
Change the way event handlers are specified, bound and unbound

Event handlers must inherit from the EventHandler base class.
Event objects are preferred to bare functions because they save
you from using global variables and binding the same function
repeatedly for different functions.
See the tic-tac-toe demo for an example.
Wrap event handlers in an event class following new change

Simply placed the logic in the bare functions in the ::handler
method and changed the global variables used earlier into class
fields.
Change README code example and remove earlier indentation

The earlier example was stupid and a bit childish. The new
one is a little bit more practical.