This changeset improves the ergonomics of running the Nomad e2e test
provisioning process by defaulting to a blank `nomad_sha` in the
Terraform configuration. By default, a user will now need to pass in
one of the Nomad version flags. But they won't have to manually edit
the `provisioning.json` file for the common case of deploying a
released version of Nomad, and won't need to put dummy values for
`nomad_sha`.
Includes general documentation improvements.
This change allows for providing the -suite=<Name> flag when
running the e2e framework. If set, only the matching e2e/Framework.TestSuite.Component
will be run, and all ther suites will be skipped.
