* cleaned up error module:
- only one template
- save error message in xml and reload
* better display of problem definition and metadata to staff
* save error messages as string, not exception objects.
* simplify logic--tracker just tracks errors. Trackers should not raise,
and are not be responsible for logging.
* adapted code to use trackers.
* Started cleanup of error handling code:
- if need to add info and re-raise, just do that. No logging.
- if working around a problem, log and track as needed.
