mvn message module : cut circular dependancy w/ core + merge sub-modules

Core module currently depends on resources located in the messages modules (hidden dependancy), while messages module depend on core module (explicit dependancy).
This prevent from importing in Eclipse IDE without manual operations.

The object of the ticket is to check if :

• Dependancy can be declared such as core depends on messages, while cutting dependancy from messages to core
• Make one single message mvn module