make -sources and -javadocs for all Jars, and only when -Pdeploy is set.

Two changes here:

1) The native-jars now have a single Java class in them to force the
creation of the -sources and -javadoc jars (which are required for Maven
Central deployment).

2) Our parent pom now only does -sources, -javadoc and GPG signing if
we've set the Deploy profile. That way we save a few seconds in what is
already a laborious build.