Allow creation of exceptions with PREPARE type

Author: rakillen

core/src/main/python/wlsdeploy/exception/exception_helper.py

@@ -40,6 +40,7 @@
     ExceptionType.DISCOVER:              'create_discover_exception',
     ExceptionType.ENCRYPTION:            'create_encryption_exception',
     ExceptionType.JSON:                  'create_json_exception',
+    ExceptionType.PREPARE:               'create_prepare_exception',
     ExceptionType.PY_WLST:               'create_pywlst_exception',
     ExceptionType.TRANSLATE:             'create_translate_exception',
     ExceptionType.VALIDATE:              'create_validate_exception',