Pulled ENAMEX processing out into more general XML-ish processing

This will be handy for .coref documents, which are in a similarly annotated text format.
Added token calculation to AnnotatedText and ENAMEX.

This implementation is probably not particularly efficient, but it seems to work
(passes the accompanying unit tests, anyway).
Renamed test 'enames' package to 'enamex'
Added EnamexIteratorTest

Also changed LineIterator dependency to Iterator<String> for the line-based iterators