Improve clicky table generation.

Disentangle the CSS rules for clicky tables from the file listing table
type, and eliminate all id selectors in favour of class selectors.

Then, move all the support markup out of the eruby program and into a
dedicated XSLT program which will perform the necessary transformation
based on a couple attributes added to the table elements.  The inputs,
labels, and the links between them are now automatically generated.

While it's more code overall, hopefully this reduces the complexity
of the implementation by clearly separating the various different parts.
Additionally, this should (if ever needed) make it easy to add clicky
headers to other tables, as well as supporting more than one clicky
table on a page.