Rule pretty print feature
Rule application tracking
Zombie-monitor issue fixed
Debug Monitor implemented
Node debug mode
Debug output format improved
Minor debug output format improvements
Various debugger minor improvements
Packrat cache bugs fixed
Syntax error output minor bug fixed
Node hashing; Node print format improved
Smart node merging feature; Token Reference bug fixed
Node merging minor improvement
Merge branch 'syntax-debug'

 - New features:
   - Debug Monitor that shows parse steps of the selected parse rule.
   - Node smart merging. Now merging procedure reuses branches of the previously
     parsed node.
 - Minor improvements:
   - Nodes support hash function.
   - Rule pretty printing.
 - Bug fix:
   - Zombie-monitors removing.
   - Major issue in Packrat cache fixed.