Bring yang-model-validator suite/lib up to date

Bring yang-model-validator suite/lib up to date

- using new version of the yang model repos to run the
  tool against.
- removed all files/paths for models that will fail
  validation. Each file removed was seen to have
  failed for what looked like valid reasons with
  a few exceptions which will be opened as bugs
  against yangtools to double check the results.
- moved keywords to the main test case to prevent the
  need for SUITE variables. This resulted in the loss
  of a full test case which was not really a test
  case and only collecting a log file when a failure
  happens.
- added more docs to hopefully help the next
  maintainer that works on this suite.
- modified docs to reflect the new state of this suite

JIRA: INTTEST-80
Change-Id: I08815cd10de7ad97745688d50c7f8ed37f9aebbd
Signed-off-by: Jamo Luhrsen <jluhrsen@gmail.com>