change the way the app closes

[oakmac]

This is an internal architecture enhancement.

Right now the app closes the "catch" event at the browser side, prevents default, and then sends an IPC signal to the window side in order to show the shutdown screen and kill any existing Leiningen processes that may still be running.

The problem is that if the window app reaches an invalid state (happens all the time in development), then you have to force-close the app in order to get it to shut down because the normal close event is always being trapped and waiting for the "shutdown-for-real" signal (which will never arrive since the app is in an invalid state).

In theory this should never be a problem, but in practice it seems to happen often. It's embarrassing that you have to force-close the app in this way when it breaks or encounters a bug we haven't anticipated.

We need to change the way this works so that it's easy to close the app when something breaks.