Clean-up version properties in kie-parent-metadata

 * use kie.version property as default for others like drools.version
   and jbpm.version.

 * the kie.version is also used for kie-bom to be able to change
   version in submodule without interfering with the version of
   kie-bom (before, the version could not in fact be changed,
   unless the kie-bom was also released with that updated version)
leave droolsjbpm-integration as is for now, as it's not been renamed to kie-integration (yet?), it's kinda still owned by drools :)