In rare cases (one known case) sizes of areas used as container when spreading
footprints can become negative, thus hanging pcbnew.
Happens if many footprints are very big (say 80cm).
Now if there is no room to place footprints, some are stacked.
This makes zoom automatique work much better in the footprint
editor, and should improve other things which probably assumed
the bounding box included everything (such as refresh code).
Callers which still want just the module outline should call
GetFootprintRect() instead of GetBoundingBox().
BOARD::GetBoundingBox() now directly calls BOARD::ComputeBoundingBox()
and there is a new method BOARD::GetBoardEdgesBoundingBox() used for
call sites that needed to use ComputeBoundingBox( true ) in the past.
This allows COMMON_TOOLS to implement ZoomFitScreen without knowledge
of the BOARD class.
Now footprints, after loaded by reading a netlist are grouped by sheets by the footprints spread function, and the grouping is better.
Rename 2 files. Fix minor issues. Clean code