Running non-root

As with many Rails applications, Radiant has the odd glitch when asked
to run from a non-document root location. I’m serving Radiant from
/rails/radiant at the moment. After the usual updates (prefix all
routes, set asset_host in environment.rb, set a unique cookie prefix
there too to avoid collision with other apps on the same host)
everything works, except <r:link>-generated links. These are created
relative to the host document root.

I’m happy to fix this and produce a patch but after a brief look around
and some head scratching I couldn’t quite figure out which files I
should be changing… All pointers appreciated :slight_smile: