Towards 0.2 --

Towards 0.2 --
	- Fix the order of proximity parameters in accordance with the
	  updated official grammar, which now specifies proximity
	  operators of the form
		prox/<relation>/<distance>/<unit>/<ordering>
	  as in ``foo prox/<=/3/sentence bar''.
	- Make the necessary parts of the CQLNode class and its
	  subclasses public.  This means that client code can now walk
	  through parse-trees and so implement its own back-end
	  (e.g. to build BER-friendly data structures using whatever
	  Z39.50 toolkit is preferred.)
	- Add javadoc comments for CQLNode and subclasses.
	- Add the toPQF(Properties p) method to CQLNode and subclasses.
		(### NOT YET FINISHED)
	- Add UnknownQualifierException and UnknownRelationException.
	- Add "-p <props-file>" option to the CQLParser test-harness,
	  indicating that the parsed tree is to be rendered to PQF.
	- Add etc/pqf.properties to configure to toPQF() method.
	- Rename ParameterMissingException to MissingParameterException.