Repaired bug and check if FA is empty or wrong.

* When checking equivalence FA without start state or final states there was bugs in algorithms which cant work with this non ended FA.
* When Finite automata is empty there is special icon with excremention mark (not false icon).
Refaktoring. Add first example. Bug repair.

Repaired bug in function QModelIndex RegExpTreeModel::indexFromNode(RegExpNode *node) const!
Added RegExp to FA Examples and bug repair.

Also added:
 * RegExpToFa refactoring and add support for advanced and more user friendly logic.
 * Add empty RegExp functionality as empty set prepresented by empty set sybmol.
 * Finite automata:
	* new function bool hasEpsilon()
        * bug repair in function FiniteAutomata FiniteAutomata::toMinFA(FiniteAutomata FA)
 * Programmaly check action so user can see which mode was selected.
 * Add new unit test for RegExp("a+b") to FA