[Feature] Display a dialog with post-install instructions

[linuxgurugamer]

I'm going to be including AutoPruner with a mod (once the author gives me permission) because this mod will be disabling another mod, but using the parts in that mod.

So, I've gotten the netkan working properly, and tested it locally. I'd like one of the following available:

1. Have CKAN run an embedded command in the netkan file (somewhat dangerous) or
2. Have CKAN display a dialog giving the user post-install instructions. In my case, I'd like to display a file which would walk them through running the AutoPruner program .

[mwerle]

In general very good idea (I've thought about something similar, shipping a small script/utility to update a save-game), but in general as far as popping up dialogs etc on install, see my more detailed reply in issue #837 .