No crash handler for Minecraft

[Pyker]

Currently, if Minecraft crashes for any reason, no error message will show up. Minecraft will simply close. The launcher, if configured to stay hidden in the background, will simply pop back up after the MC process exits.

We should tap into the existing code to create a crash handler for Minecraft, even if it's a simple "Minecraft has crashed" message that also brings up the console (to show the MC log itself).