Always use RFC3339 for version date format.

Fixes #695 reported by @synful.

- No longer tries to load a configuration.
- Because of this the version tests are no longer necessary.
Fix various Windows-issues

File handling was broken on Windows. This commit contains a revision of the path handling with separation of file paths and urls where needed.

There may be remaining issues and there may be better ways to do this, but it is easier to start that refactoring job with a set of passing tests.

Fixes #687
Fixes #660