Catch and report driving agent errors properly during a race

[Henrik Heimbuerger]

When an error occurs in a driving agent (might be as simple as a compilation error due to incorrect syntax -- or something more dynamically) a standard exception handler message box pops up. That message box is fine for internal JaCaVi errors (which are really just bugs that need to be fixed), but shouldn't be used for driving agent exceptions which can be 'expected' during the development of a driving agent.

A more sophisticated way of displaying those errors needs to be discussed and implemented.