v2.0.0-rc7

Incremental release from rc6 preview. Contains the following enhancements:

• new hook updated to support all v2.0 functionality

• Fix aws blobstore missing in new and network check

• Correct service discovery feature was missing

  If you specified outdated methods of turning on service discovery, the
  blueprint script would tell you to use enable-service-discover while
  making the change internally for the current run, but the correct
  version was not actually ever whitelisted, so if you did correct it, it
  would just fail.

• Add vm extensions check

• Initial WIP for upgrading from 1.x versions

  • Migration of vault to credhub hook
  • Check will see if the previous version is too old, and should check if
    the secrets are in the vault (TODO)
  • Blueprint will add the manifest fragments for migrating
  • Pre-deploy will move the secrets to credhub (and whatever else it
    needs to do)