Add an option to suppress the attempt to create boilerplates

[weilu]

No description provided.

[timoxley]

Great idea. Creating magical file seems bad though. Should probably go in datadir and also include direction to some command that will disable it. Maybe also provide an "always". If this is too much work though I'll just merge it as is.

[timoxley]

Note it should only be asking this if the user is missing files that exist in the boilerplate. Can you elaborate on the scenario where you want to have files in your boilerplate but not in the user's solution?

[weilu]

I also have boilerplate in my problem descriptions. Some users may want to just copy those and create their own files instead of having folders created for them.

[weilu]

I'm happy to move the file into datadir. always may not make sense because the generator generates boilerplates for all exercises at one go, so once it's there, the user won't be asked again.

[timoxley]

Sounds good. I suggest passing the "adventure" instance to setup.