fix for OODT-787 PGE_ROOT env variable does not work in PGEConfig.xml and tasks.xml contributed by Yi Sun <Yehudi@Yis-MacBook-Pro.local> this closes #12

git-svn-id: https://svn.apache.org/repos/asf/oodt/trunk@1638737 13f79535-47bb-0310-9956-ffa450edef68