The `params` vs. `bind` class distinction has been blurry for a long time. I'm
formalizing it.
`params` is now `defaults` and its purpose is to gather platform-specific
variation into a single scope. These variables are related to situating a BIND
server on a particular platform and it should not ever be necessary or perhaps
even possible to change them as a matter of preference. Rather, correct values
are function of e.g. `$osfamily` or `$operatingsystem`.
The parameters of the `bind` class are limited to those that control the
server's feature set. These parameters *are* matters of preference and/or
purpose, rather than platform.
Also, I have taken some care to develop a convention for direct references to
qualified parameters where they are re-scoped into the local scope centrally at
the top first, and subsequent references are to the local value. This should
minimize future code churn and also aid readability.
Fix a bunch of warnings whne using the bind::updater class by moving confdir to
the params class. In order for this to work, the bind and bind::updater classes
both now inherit from params. Also, fix the default value for
managed_key_directory to something that's actually falsey.
