[keycloak-dev] Remove Arquillian from testsuite

I'm thinking about removing Arquillian from the testsuite and use AbstractKeycloakServerTest instead. This removes the requirement of having JBoss AS available to run the tests, and will make it simpler to have the testsuite run as part of a regular build. I've already removed Arquillian Drone and Graphene, as they didn't really provide that much value-add. Any objections?