refactored - improved the graphics package to make it run
more efficiently and contain less, but more readable, code. The plots
now only handle Complex numbers. Both the 1D and 2D plots are now
extensions of Plot.
improved - added a another plot to the QFTSandbox, representing the
total probability of being in one of the higher particle number states.
improved - removed all the unnecessary functions from State and made the
BaseState implement it directly.
deleted - the Graph class was removed since its job is better handled by
the Plot, at a later stage (it was currently unused). Also the
DoubleBufferedCanvas was removed since its functionality was taken over
by the Plot abstract class.