Add multi-tenant principal codec for Automation

As we cannot unmarshall correctly the nuxeo principal (org.nuxeo.ecm.platform.usermanager.NuxeoPrincipalImpl#getTenantId returns 'null'), we need to include in the multi-tenant addon a way to marshall/unmarshall all the information of a org.nuxeo.ecm.multi.tenant.MultiTenantPrincipal.

-> Add an Automation codec for org.nuxeo.ecm.multi.tenant.MultiTenantPrincipal