Adds comparator for control graph domains

This helps graph visitors to return contents in
the natural order by increasing domain offsets.

Issue: #32
Rewrites graph visualizator using graphviz

*nix way rocks!

Issue: #32
Moves some code of TSmalltalkInstruction class from headers into .cpp file

Removes TInstruction from types.h.
Adds method TSmalltalkInstruction::toString().

Issue: #32