[development] register the install profile in system table?

[Nedjo Rogers]

> In general...it will allow for versioning. We're really just at the early
>stages of this...need to get a couple out in the wild. This just "feels"
> like the right solution...

That's what I'm feeling.

I've roughed in a patch at http://drupal.org/node/80272. The main change is 
generalizing the various schema-related functions. Currently they assume 
we're talking about modules. So we introduce a $type argument, so they can 
be used for whatever system item type.

Anyone able to give this a review? Does this sound like the right general 
approach? Thanks.