RFC: TopicBasedHelp specification

[Matthew East]

Not a lot of discussion has taken place recently about this spec. I've
gone ahead and made some changes to the spec itself, to try and:

1. Demonstrate how this spec can be a Kubuntu spec too, not just Ubuntu.
2. Add some concrete implementation suggestions.

https://wiki.ubuntu.com/TopicBasedHelp

I'd really like to see feedback from the authors, in case my edit has
moved the spec away from the place they had envisaged... I don't think it
has, but you never know.

Hopefully if we can arrange a meeting, this spec can be discussed in the
light of some concrete proposals for implementing it.

Matt