Adding an Exception-logging command excecution hook

This only attaches to the exception-during-run phase and passes the
Exception off to the supplied ExceptionLoggers, which will log the
Exception if they can.
Created DBI and SQL ExceptionLoggers
Defensive copy of ExceptionLoggers and application of generics
Adding command execution hook to tenacity bundle builder

Optionally registers the execution hook if it was set by the builder
Merge pull request #2 from thesmith/master

Adding an Exception-logging command execution hook