Fixes whitespace problems with executing maven from ant

* build-common.xml
 * check for ant-contrib and download from sourceforge if necessary
 * removeWhitesapce macro for removal of extraneous whitespace in property
   values provided to it
 * Executed mvn with whitespace-handled arguments

* build.xml
 * Fixes whitespace issues with both libs and parsers properties
 * Instead of executing 4 separate mvn instances, execute only one using
   the pl switch to delineate the projects to build
 * Instead of calling mvn clean which requires the should-generate flag,
   simply remove the generated parser files. Faster than using maven.
 * create a clean-internal target that is only executed if the
   should-generate property is true. Use the clean target for executing
   regardless of the property and removing the generated parser files