Add files with static constants for use as keys to the package settings

I gave engine a file that holds the package settings it knows about and console a file that holds both those settings and the driver settings.

This is likely to be a temporary fix, but it eliminates a lot of string repetitions and makes it possible to find all references to a given setting - unless I missed some, of course. It's worth merging now.

I think the final resolution for this may be to figure out a way to give TestPackage real properties without breaking version-independence. I'll start a separate discussion of this issue on email.