Move spec org/group/status info to a config file

[tabatkins]

Currently, info about what Groups and Statuses exist, and which groups are part of what org, etc. are all tracked in some Python data structures in config/status.py, meaning I have to roll a new version of Bikeshed whenever someone adds a new Group to the boilerplate repo and wants it to be recognized as a W3C group or something.

This change moves those data structures into a config file, boilerplate/doctypes.kdl, which now lives in the bikeshed-boilerplate project. It also significantly restructures how I deal with the information previously in that Python file.

• I reify the concept of an "org", previously a special case just for the W3C and implied in the "canonicalized" form of the status shortnames. An org contains 1 or more groups and 1 or more statuses, and namespaces both of them. You can set your org via the new Org metadata, or imply it by using a Group or Status with it as a prefix, like w3c/wd (implying Org:w3c and Status:wd)
• Org, Group, and Status are now data structures, not just strings, and live on the Spec object collected in a Doctype object, rather than in the metadata. (The metadata still contains the strings that were passed, of course.) This allows for easier normalization and regularization of access, fixing some bugs I didn't realize I was experiencing (wrt casing of values, and "canonicalized" vs un-.)
• Previously I allowed unknown Groups; I now emit an error in that case. I think it's more useful to know if you're using a known Group value or accidentally have a typo or something. It's very easy to add new Groups now, and if you don't have Group-specific boilerplate you don't even need to say anything; just the Status and possibly the Org is enough.