Add the Nuxeo bind address as default trsuted host in the OpenSocial Service

A default trusted host will be computed from the Nuxeo bind address:

• 0.0.0.0 -> localhost
• any other IP will remain unchanged

Add a new property in nuxeo.conf 'opensocial.trusted.hosts' to be able to configure other trusted hosts. The default trusted host computed from the nuxeo bind address will be added to this list.