From Symbolic DFA to HOA

**Is your feature request related to a problem? Please describe.**
It is missing a proper way to represent an automaton in a specific format. HOA format seems to be a pretty standard approach for that: http://adl.github.io/hoaf/

**Describe the solution you'd like**
Support conversion from DFA to HOA.

**Describe alternatives you've considered**

**Additional context**
