cleanup
cleanup

refactoring: modularized MouseTracker

cleanup
bugfix: line end attach / detach is now undoable / redoable
add / remove diagram elements
added style specs
added 'assembly' option to build
style repository
bound shape specs to style specs
init of SelectedStyles based on style repository
fill style editable for boxes (*very* rudimentary implementation)
styles changeable via 'property' forms
cleanup
line end 'arrow points' are now selectable
cleanup
very raw initial version of 'load' and 'save'
cleanup
cleanup
cleanup