wiki/markdown: image references

[cooper]

Maybe relative images in markdown should be symlinked to the actual image directory of the wiki.

[image](image.png)

might do like

ln -s /whatever/the/markdown/file/base/is/image.png mywiki/images/image.png

if that file exists at generation time and an image by that name doesn't already exist in the wiki.

This could be a configurable feature.