ui.components.Category*: handle item selection
VirtausWindow: first iteration of ProductPanel
ProductPanel: the first working commit (still a lot of work to to)
Product: getCollection() method implemented
CategoryView: implemented selection modes
ProductPanel: fixed wrong use of DiagramView
CollectionPanel: fixed wrong use of CollectionView
DiagramView: implemented necessary methods
DataProvider: now using single-instance (singleton design pattern)
DataLoader: fixed static functions
DataRegisterer: implemented createCollection() method
DataParser: moved writing code to DataRegisterer
VirtausWindow: implemented ProductPanel
DataRegisterer: working code!
DiagramView: implemented product's item selection
NewCollectionDialog: fixed lack of information fields, now really creates a collection
DataParser: link root element to the document
DiagramView: fixed selection code
VirtausWindow: fixed code order
Item: fixed isTexture() method