jcr2vfs: add distribution module

 * the distribution module basically bundles together
   deps for importer and exporter and adds sh/bat
   script that will the migration in two phases

 * only this module should contain any sh/bat scripts
   to avoid unnecessary maintenance of additional
   scripts in importer/exporter
jcr2vfs: make sure correct versions are always used in JCR exporter
jcr2vfs: clean-up dep. mgmt. in parent pom
Merge pull request #1 from psiroky/jcr2vfs-assembly

Distribution assembly for jcr2vfs tool + some related changes