Improved expression tokenizing
Added expression to value enumeration
Added tokens for enumeration values to ensure they were capitilized in the xml
Allow for empty blocks in mapfile
Fixed errors in xsd file
Moved xsl and xsd files into a data directory

Doing this made sense because they are not just copies of the MapServer provided xsd and xsl anymore; they have been changed (improved) to work with
the output of map2xml.