[PATCH 0 of 3] Html help in hg serve when docutils is available.

[Erik Zielke]

This patch series contains of three patches:

- First two patches refactors the code to generate html help, so it
  can be used by 'hg serve'

 - Third patch uses this to generate html help in 'hg serve' when
   docutils is available, otherwise as before.

This requires a change in the templates. I have only edited the paper
template, because would like to get comments before I edit the others.

I am not too happy about the line with html tags in the code, another
solution could be having to keywords in the template, e.g. doc and
htmldoc, where there is always only one of them that is not an empty
string. Better solutions? If not, which of them is best?