diagram: trying to implement next step (boundarySetsStep2), with dependencies
diagram: trying to implement next steps
some more stuff
rendertest: moved some code to graphical/

--HG--
rename : rendertest/drawtools.go => graphical/drawtools.go
rename : rendertest/shape.go => graphical/shape.go
(go fmt)
graphical: extracted Diagram from rendertest/

--HG--
rename : rendertest/stackblur.go => graphical/stackblur.go