ebean: remove Ebeanby.packages method

[jknack]

Prefer the callback way:

{
  use(new Ebeanby().doWith((ServerConfig ebean) -> {
    ebean.addPackage("foo");
  }));
}

The packages method isn't used it and makes thing a bit harder from implementation perspective:

{
  use(new Ebeanby().packages("foo"));
}