Pome JS tests now part of build

Moved rdf/src to rdf/rdf_common_jvm/src so that IDE's work nicer. Otherwise, I have just got pome compiling OK and the tests pass.

I have also used my plugin https://github.com/InTheNow/sbt-scalajs that allows scalajs to test and compile as per a scala project - i,e

sbt test
I think that as far as tests goes its very important to have plantain and pome in the tests that are run, so that these projects don't drift. Of course this does not mean they should be published. Can we remove them from publication without removing them from tests?