#1 Hard to tell when game editor has finished compiling

[Karl Gluck]

Because it launches in a separate thread and provides no notification of completion, it's hard to tell when the editor finishes compiling. It should:
1- Disable the "compile..." menu item until it completes
2- Compile to temporary files first
3- Only display the "save as..." dialog boxes once compilation has succeeded, so that the user can save out the results