Implementation of Features from #489

[koniksedy]

This PR extends the functionality of print_to_dot. And closes #489

It now:

1. Merges multiple edges between two states and places a list of labels on the merged edge.
   Optional:
2. Collapses contiguous sequences of symbols in labels into intervals.
3. Truncates long labels (the full label can be seen when hovering over the edge).
4. Removes all labels.

[Adda0]

LGTM.

[jurajsic]

This can be simpler:

Suggested change

	switch (symbol) {
	case EPSILON: return "<eps>";
	default: break;
	}
	if (symbol == EPSILON) {
	return "<eps>";
	}

[koniksedy]

I know. I put the switch there on purpose, so when we introduce new — I don't know how many — symbols, it won't become a mess of if-else statements.

[Adda0]

Can we merge this PR, or do we plan to work on this more?

[koniksedy]

It's done. We can merge it.