R1:57a9c3f07c6a

Improve Diviner handling of paths and remarkup

Summary:
- Currently, the atomizers don't emit atoms with the right file in all cases. Make them always emit it correctly.
- Currently, we use absolute paths in some cases and relative paths in other cases. Use them consistently: relative when storing/presenting, absolute when accessing data.
- Don't preserve linebreaks when marking up documentation (documentation is generally wrapped at 80col, but should not be wrapped in this way when displayed).