Parser now handles basic cases, with default error messages
added finish messages to Parser, as well as the ability to reset()
enhanced character set formatting to group characters in a range
start of regexp declaration of Nodes
wip: investigating implementations of IdentitySet, this version is twice the speed of HashSet (but trades that off for memory)
settled on a version of IdentityHashmap optimised for a small number of elements; which is 2-3 times faster than the JDK HashSet.  However as the number of elements increases, this version gets much worse.
created NodeFormatter, very useful for creating expressive unit tests
created ConstantOp, the simplist of the regexp factory ops
added zero or more regexp op
added or regexp op
added and, and oneOrMore regexp ops