Specifying a whitelist should make blacklist default to everything.

[analog-cbarber]

If you have specified a whitelist, then an empty blacklist doesn't really make any sense.

Instead if there is a whitelist perhaps the blacklist should default to everything if not explicitly
specified.

To make such a change backward compatible, we could add additional names to use for
blacklist/whitelist (probably a good idea anyway) and only apply the new behavior to the
new names. E.g. 'exclude' for 'blacklist' and 'include', 'require' and/or 'depends' for the whitelist.

[xhochy]

👍 This could be done with regards to what is already open at #11