RegexpParser can now recognise nested expressions using the syntax $name.  It does not however support recursive use, yet.
moved trie code into the parser code base; keeping the two separate has no longer become practical as the cleanest way to manage embedding of the graphs is via the regexp part of the parser
removed <T> from Node and Nodes.. hard wiring to be parser specific
relocated ParserFrameOps from ProductionRuleBuilder
added ability to nest ProductionRules