[VVP] Preload Generation Enhancements and Fixes

[VVP] Preload Generation Enhancements and Fixes

- All values flow to preload env templates (availability
  zones were not)
- defaults.yaml should be in preload_env (includes vnf_name)
- Ensure SDC Model Identifiers are documented in VNF API format
  (ex: vnf-type, etc.)
- Ensure CSAR is used in VNF and GR API where appropriate and available
- Flag populated preload templates with _incomplete when they are not
  fully resolved
- If a value is still set to CHANGEME in the preload env, then revert
  to the original VALUE FOR from the blank preload template
- Ensure app_tests/preload_tests/sample_heat passes all vvp validations
- Added missing depedency (bandit) to requirements.txt

Change-Id: Idf1d5e6e5237debcf3e94bed5fcf7c15e41c9e82
Issue-ID: VVP-283
Signed-off-by: Lovett, Trevor <trevor.lovett@att.com>