Fixed LinkedItem bug. Using T* instead of a concrete type.
Commented out old stuff in Widget.{h,cpp}

Ready to start using linked items.
Must implement most methods.
Major commit 5/05/2014.

Reimplemented Widget base class.
Using LinkedItem to store child widgets.
Precalculating widget window coordinates.
Precalculating lists of visible widgets.
Rendering only visible widgets.
Delivering events only to visible widgets.

A lot of small fixes here and there.

No scaling for now.