Fix templating to return correct mime types and do safe html/xml escaping

This should also fix #126. The problem was that the template system
was set up for html only and so would produce the wrong mime type when
used for text templates. We now pick the mime type and the escaping
mechanism based on the template file extension, .html.st vs .txt.st

So also have to rename some templates that were not following the naming
convention.

Also use more template type instances to simplify the code where do the
template substitution.
Build dependencies seperately so they don't contaminate docs.tar (fixes #130).
Allow more names for changelog files

Including none, .txt and .md extensions. But don't use .html
fix templates file glob
Add more allowed file names for changelogs

Based on byorgey's pull req #149
Merge pull request #153 from horus/fix_data-files

Fix templates file glob
Merge pull request #150 from komadori/issue130

Build dependencies seperately so they don't contaminate docs.tar (fixes #130).
Clarifiy allowed chars in user names

We now allow '_' in user names, and the page now says symbols are not
allowed, except _. Fixes #154.
Merge branch 'master' into central-server