Exported the Package which is imported in SCTUnit.test

The Package is needed to create a MsgPredicate

test-plugins/org.yakindu.sct.generator.genmodel.test/META-INF/MANIFEST.MF

@@ -25,3 +25,4 @@ Import-Package: org.junit.runner;version="4.5.0",
  org.junit.runners;version="4.5.0",
  org.junit.runners.model;version="4.5.0",
  org.hamcrest.core
+Export-Package: org.yakindu.sct.generator.genmodel.test