Remove chef, habitat, puppet, and salt-masterless provsioners,
which follows their deprecation. Update the documentatin for these
provisioners to clarify that they have been removed from later versions
of Terraform. Adds the fmt Make target back and updates fmtcheck script
for correctness.
The main motivation here is to produce a helpful error if a user
incorrectly uses the terraform-provider- prefix (which we see on provider
VCS repositories and plugin executables) as part of the source address.
However, this also more broadly blocks "terraform-" as a prefix in
anticipation of whatever instinct causes the phenomenon where e.g.
Python's PyPI has thousands of packages whose names start with "python-",
even though everything on PyPI is for Python by definition. This is
definitely not _necessary_, but it's better to be restrictive at first
and weaken later as needed.
With provider dependencies now appearing inside a nested block, it seems
likely that configuration examples showing dependencies out of context
will sometimes mislead users into thinking that required_providers is
toplevel.
To give better feedback in that situation, we'll produce a specialized
error in that case hinting the correct structure to the user.
Pam Selle