Clean urls for wiki docs

Because creator will invest 1000s of hours building content on wiki docs, HB cannot be the source of truth. Having a good export/import roundtrip (to markdown) is a big must. that would require using clean urls (and the file names being the titles). Otherwise we'd be stuck in vendor lock-in.
Given how the new 'courses' functionality will use wiki docs heavily, and people building a CBC will rely heavily on these, it's time to build up the best wiki docs possible :)