[keycloak-dev] added a keycloak-common module

The SAML adapter had some dependencies on classes within keycloak-core. Unfortunately though, keycloak-core brings in Jackson JSON parser. So, I split out keycloak-core into keycloak-common and keycloak-core. PR is pending, but it should be in when the Europeans wake up. -- Bill Burke JBoss, a division of Red Hat http://bill.burkecentral.com