ItemSelectionListener: created interface
SelectedItemEvent: created event
MainWindow: prepared to receive the other panels
MainWindow: fixed hidden panels not showing - needs resizing to do it (phew! took effort, hã)
CategoryDataPanel: created CategoryDataPanel
CollectionView: fixed typos
CollectionItemList: first working code
CategoryView: working code
DiagramPanel: small fixes
ProductPanel: no code at all (todo it)
SepiaFilter: created SepiaFilter (don't know if it works though)
GrayScaleFilter: implemented MaximalDecomposition and MinimalDecomposition algorithms
FilterFactory: added SepiaFilter