RFE: add lsb specification autobuilder

[Jeff Johnson]

Filed after brief IRC discussion.

It might be worth adding a buildbot task for building the LSB specification
documents. Currently the build happens in two separate branches, "books" and
"booksets". There's puppet magic to populate the spec snapshot directory from
these two branches, but the builds happen only manually.

Note the book build is different from regenerating/updating the specification
itself, that happens in the lsbspec tree and should probably remain a
manual-only process, since changes should be examined before committing, and
since a full database setup is needed.

I don't think we have a buildbot task which actually commits to bazaar, so this
might be a little odd.

If this is done, it should probably be supported by a reorganization of the
built books, so that all the ones which are "potential specifications" are all
built in the same tree. At the moment, as noted, they're split between two
trees, using the somewhat unscientific method that if a book combines several
modules, it's called a Book Set and goes in the booksets, if it's a "single" it
goes in books but still gets an LSB- prefix.