Remove unused class ParserATNPathFinder
Remove unnecessary method ParserInterpreter.predictATN
Remove unused and undocumented method DFA.getATNStatesAlongPath
Cleanup and encapsulation in LexerATNSimulator
Improved encapsulation in ParserATNSimulator
Updated documentation for addDFAEdge and addDFAState
* Simplify creation of new DFA edges - only create the target state and let DFA code check for termination conditions

* Fix handling of previously cached error edges (always need to check previous state for reaching a rule stop state)
* Fix DFA created during SLL-only parsing (should be identical to the DFA created by full LL parsing)
Extract methods getExistingTargetState and computeTargetState
Add TestPerformance.COMPUTE_TRANSITION_STATS
Remove unnecessary null checks
Merge pull request #235 from sharwell/prediction-fixes

Prediction fixes