Refactor extract support for mapping Jackson JsonNode into separate module - ebean-jackson-jsonnode

[rbygrave]

Apps depending on the io.ebean:ebean composite will still get this as a transitive dependency and will see no effective change but otherwise apps that depend on the platform specific composites like for example io.ebean:ebean-postgres will now need to explicitly choose to include support for mapping Jackson JsonNode by explicitly adding the dependency:

<dependency>
  <groupId>io.ebean</groupId>
  <artifactId>ebean-jackson-jsonnode</artifactId>
  <version>...</version>
</dependency>