Massive refactors, and general modernization.

- Rewrote opened-files.
- Access to Google Drive wrapper is now direct using wrappers (no more "drive_proxy").
- Refactored debugging (is only via variable now, not parameter).
- Now allow change-monitoring to be disabled (for debugging).
- Added protection for concurrent handles to the same file, for now.

We still need to debug truncate() call (still getting 401-Forbidden).