added setting save_all_on_build; automatically saving all UnrealScript f...

Hi!

I added a setting save_all_on_build, default: True which saves all dirty UnrealScript files when starting a build.

There already is a checkbox and a option with the same name in the default sublime workspace but I couldn't figure out how to read it. Perhaps you know how to do that and could bind the function to the already existing option?

This is a REALLY nice plugin!
Julian