BUG Exception handling and email notification mechanism now correctly considers the stacktrace as provided by the exceptionHandler function, instead of attempting to perform a debug_backtrace further down the reporting chain (which ends up generating an unnecessarily nested stacktrace). Debug was cleaned up so that errorHandler and exceptionHandler both act consistently. As a result, the LogErrorEmailFormatter class could be simplified.

This was required to fix a bug in which exceptions would not have a visible stacktrace when handled by the email logger.
Added test cases for exception error logging