[Terry N.] add workaround for differing project configs between students

assignments/nbproject/project.properties

@@ -118,6 +118,7 @@ manifest.custom.permissions=
 meta.inf.dir=${src.dir}/META-INF
 mkdist.disabled=false
 platform.active=default_platform
+platforms.default_platform.home=${java.home}
 project.licensePath=../license.txt
 run.classpath=\
     ${javac.classpath}:\