[VVP] Update validations based on VNFRQTS-637

Update to the latest bundled requirements text
Update aap_exempt message to better reflect verbiage
Remove unneeded test: tests_neutron_port_addresses (requirement removed)
Map aap_exempt requirement to associated tests

Also adding new helper scripts to help detect divergences between
VNF Requirements and VVP as well as other VVP best practices:

checks.py - Pre-commit checks
- requirements are up-to-date with VNFRQTS
- all testable requirements have tests
- all non-testable requirements are *not* mapped to tests
- flake8 passes
- self-test passes

update_reqs.py - Updates the the contents of heat_requirements.json
with latest req'ts from VNFRQTS Nexus artifact

Change-Id: Ia197de3254a1a0369224939f66a5f98c601a314d
Issue-ID: VVP-216
Signed-off-by: Lovett, Trevor <trevor.lovett@att.com>