The inventory window content is now controlled by the InventoryView
class.
Entities now have weight.
InventoryView item details is now a grid view showing item properties.
RootVisualPanel is now a singleton.  Make sure to clear it when you
leave a state, and re-populate it upon entering a state.
The heads-up display is now controlled by the HUDView class.
The HUD now has a place to store hotkey items.
Placeable entities can now be places with left mouse clicks.
Trees can now be generated using xml.