Client|LogWidget: No need to retain a static Y coordinate for each entry

The entries are rendered dynamically when needed, so there is no need
to set a static Y coordinate for them inside the virtual content area.
Fixed|libgui|Image: Filling with transparent pixels

When painting the fill, one must use the appropriate composition mode
so that alpha blending does not occur.
libdeng2: Added Range, relocated Matrix, Vector, Rectangle, Version to core
Refactor|libshell: Use de::Rangei instead of libshell's own Range
Refactor|Client: Use de::Rangei
Cleanup