improve log messages to identify configurations that are in valid

REF: https://bugs.internet2.edu/jira/browse/GRP-1558

Maybe the configuration checking process should flag settings that "don't make sense" so that the implementer could be told "x does not exist in source 'a', Please correct setting 'foo' with a valid value" message in the logs? ( Maybe a special "check config" function should do it instead of at "start up"?)

Not limited to "email", Think more generally.

Validate any "hard coded config strings" that are subject to the possibility of not being valid for use.