IRI cleanup

[Andy Seaborne]

Background: the IRI library used JFlex v1.3.4 to build java lexers. 
JFlex is GPL.  The calls to JFlex are by reflection - it's not on the 
classpath of the project.

The IRI library builds and ships with the generated (and incidentally, 
manually fixed) java.  Building the IRI library from the source-release 
does not require JFlex.

I've refactored the code used to help build the lexers into a separate 
source folder.  Now the maven build does not include even the reflection 
calls to JFlex main.

        Andy