Fix unit tests

This code has to go in JApplication base really because of the required method. Anyone extending JApplicationBase (next to 0 probability I know but...) will find a fatal error if they don't have the doExecute method now they didn't have before. I'm not saying it's ideal - but it's the b/c solution

It's also why the CMS unit tests are failing.

The classmap extra thing is also ugly but currently used here in the CMS https://github.com/joomla/joomla-cms/blob/staging/libraries/joomla/application/cli.php#L78 and again whilst we can change that (and should) it's another one of those things where if we're using it as core it really is a b/c break for that to fatal. I dunno what the PLT opinion on this is if classmaps aren't case insensitive like they were before? I kind feel like it's asking for problems?