(docs) Revise and unify explanations of module/file references in function docs
(docs) Mention file() function in file type's content attribute

Now that this function works in a more useful way, we can advertise it a bit
more widely.
(docs) Clarify note about ssh_authorized_keys in resources resource type

It's not that it's deprecated, it's that it never worked.
(PUP-2914) Remove 'gem install rgen' step now that it's vendored
(maint) Namespace constant declaration in specs to prevent warnings

Add module namespacing to two specs declaring an FS constant (for
convenience) so that we don't receive warnings about the duplicate
declaration.
Merge pull request #3021 from nfagerlund/docs_clarify_resources_resources

(docs) Clarify note about ssh_authorized_keys in resources resource type
Merge pull request #3016 from nfagerlund/docs_37_file_function

(docs) Revise and unify explanations of module/file references in functi...
(packaging) Update PUPPETVERSION to 3.7.0
Merge pull request #3037 from kylog/issue/pup-2914/remove-rgen-install-step

(PUP-2914) Remove 'gem install rgen' step now that it's vendored
(PUP-3175) Isolate yamldir for node/check_woy_cache_works.rb

Signed-off-by: Wayne <wayne@puppetlabs.com>