Refactor validate to remove overlapping / duplicate classes

[jordanpadams]

When we combined a couple codebases when moving to Github, there were several overlapping classes that do almost the same thing, but one or another has been tweaked. We need to remove all this complication. Here a couple packages that appear to be duplcates/overlapping:

• gov.nasa.pds.tools.validate.crawler <-> gov.nasa.pds.validate.crawler
• gov.nasa.pds.tools.validate.util <-> gov.nasa.pds.validate.util
• gov.nasa.pds.tools.validate.inventory.reader <-> gov.nasa.pds.validate.inventory.reader