Cache puzzle data locally?

[apmwebdev]

For offline mode to work, users should be able to cache puzzle data locally. Potentially, they should be able to do this without saving answer definitions, since those can take up a ton of space. Or maybe they should save only a single definition per answer, since that's all that is shown anyway?

It might make sense to cache puzzle data locally for performance reasons anyway. But again the answer definitions take up so much space that condensing this data somehow would probably be necessary.

Before this is implemented, need to figure out a better system for answer definitions than sending everything and only showing a bit of it.