small improvements (edited, uploader will come later)

@felixge's formidable is awesome for bulk file uploads. I implemented the API to upload to `/tmp`, next part will be moving files into tree when they are finished.

Small problem: `camp` apparently doesn't handle `enctype="multipart/form-data"`. When I try to use my uploader, `camp` complains about a lot of Unexpected Identifiers and Syntax Errors while parsing the query. See https://github.com/espadrine/sc/issues/27

Also better log output that allowed me to find some bugs, and some documentation. `SERVER.md` might go out of date very often, not sure if it's useful to keep it.

EDIT: flyby fix for #157