generateGraphWithPackedNodes added to AbstractGrammarTest
Adding the Parser interface, refactoring and cleanup. Test cases don't pass yet, but no compilation error.
DefaultSPPFVisitor is renamed to SPPFVisitorUtil and it's not a superclass of visitors. Favor composition over inheritance.
Visitors don't accept extra arguments. Accumulation and other stuff should be handled in the visitor itself.
Test case for A ::= epsilon passes.
Simple test cases added to check parse trees.
Bug in HeadGrammarSlot fixed.
ToString method in GrammarSlots fixed. Generating Java code from ambiguous SPPFs added.
Skeleton code for recognizers added.
WrapperSlot added to allow execution of arbitrary actions before and after parsing a grammar slot