ikiwiki/ w3mmode

It's possible to use all of ikiwiki's web features (page editing, etc) in the `w3m` web browser without using a web server. `w3m` supports local CGI scripts, and ikiwiki can be set up to run that way. This requires some special configuration:

- `w3mmode` must be enabled
- A CGI wrapper must be created, in ~/.ikiwiki/wrappers/
- `cgiurl` should be set to just the base of the filename of the CGI wrapper.

This ikiwiki.setup is an example of setting up a wiki using w3mmode.