Have error exit code if any internal problems occur

[mvz]

While investigating #1081, I noticed Reek can still exit with a success code when it has already printed an error stack trace. I think we should always exit with an error in that case.

[troessner]

Agreed!

[troessner]

I think we now have a much more cleaner and consistent error handling as at the time of writing this ticket.
Wouldn't it be enough to catch all StandardErrors in Application#execute, set the status and then re-raise?

[mvz]

Errors that make it all the way up to Application#execute will probably just cause Ruby to print its stack trace and exit with an error status. This ticket is mostly about errors that are logged by LoggingErrorHandler, letting Reek continue with the next file. We'll have to keep track of errors handled by this handler and have ReportCommand#execute return a failure code if there were any.