Fixed stateful07 message parsers/serializers

Fixed stateful07 message parsers/serializers

-fixed error handling of mandatory objects in message parser:
	-i.e. if PCRpt Message's report lacks mandatory object,
	the report is not parsed - error message is created and
	continues parising of remaining reports.
	-ERO object is mandatory
-removed final modifiers and changed access modifiers:
	-parser classes could be easier extended

Change-Id: Ibb09d1301128d34ef22fbe736998a70bbbfcc01e
Signed-off-by: Milos Fabian <milfabia@cisco.com>