[keycloak-dev] Support both Jackson and Jackson 2

Currently we only support Jackson, while WildFly now uses Jackson 2. This is OK for our the auth-server itself, but could be more problematic for applications (see https://issues.jboss.org/browse/KEYCLOAK-811). The main reason we can't use Jackson 2 is that they have changed the package for annotations (@JsonProperty). I propose we get rid of all @JsonProperty and instead make sure all fields are named correct and that we set the LowerCaseWithUnderscoresStrategy on the ObjectMapper. This should also make it possible to use the Java classes with other JSON libraries. For example: @JsonProperty("access_token") protected String token; @JsonProperty("jti") protected String id; Becomes: protected String accessToken; protected String jti;