fix for Jython flask reload subprocess issue https://gist.github.com/pao...

This is a fix for the Jython reload issue here: https://gist.github.com/paolodina/b98c3f3a159024584e13

If sys.executable is blank in restart_with_reloader(), it checks if the platform is Jython and then gets the java executable information.

I apologize in advance if I've messed up on any protocol in this pull request - it's the first one I've done.  Not sure if I needed to put the work in a new branch or not.