Add a page for displaying messages sent/received by the simulator

In simulator-parent, entities and XHTML templates have been developed (see SIMUCMN-3)
In order to test this implementation, I have begun to extend this work in SVSSimulator.
Remaining tasks are:
- improve the validate() method in order to have a correct validation process there (see TransactionInstanceDisplay.class)
- nicely display the message content and validation result (see /messages/messageDisplay.xhtml)