After initialization, either warn user to install something or make GDF

[Iritscen]

Currently the AEI does not create the GDF upon init.ing. It then finishes and waits for the user to do something. If the user is a little confused and hits Run Oni, he gets even more confused when Oni won't run (correction: Oni does run because it looks one level up when it doesn't find AE/GDF and latches onto Oni/GDF; thus it runs vanilla Oni, guaranteeing to confuse the player).

The simplest option, a bit hacky, is to show a dialog saying "You need to install something before you can play Oni." (AEI1 used to say "Done! Now select your mod packages and click install.")

A better option is to do a preliminary installation, with the core packages in place for a "virgin AE" experience, and then only after that allow the user to take some action, whether it's running Oni or picking more mods to install.

[Iritscen]

Added "correction:" to descrip. Removed third option that I mentioned, because it would be identical to the current behavior (running Oni after init.ing gives you vanilla Oni).

[Iritscen]

Actually, an even better option is to ask the user after init.ing something like, "Do you want to play AE Oni now, with just core mods installed, or do you want to choose some mods to install first?" And then let them decide whether the AEI should be spending that extra time building a virgin AE GDF or letting the player choose mods and then hit Install himself.

Additional recommendation, no matter what approach you take to the above issue: Disabling the Run Oni buttons as long as an AE GDF does not exist.

[alloc]

In 810:

AEI2.03:

• Fixes #7
• Fixes regression introduced by fixing #8