Public/documented API to get cache contents

[Socob]

It would be nice to have a clear way to get a function’s cache. I see there are functions get_cache(), get_caches(), and find_caches(),

https://github.com/marius311/Memoization.jl/blob/7d183e2594b65effe98f75d564dbbd59cd881cf9/src/Memoization.jl#L30

https://github.com/marius311/Memoization.jl/blob/7d183e2594b65effe98f75d564dbbd59cd881cf9/src/Memoization.jl#L50

https://github.com/marius311/Memoization.jl/blob/7d183e2594b65effe98f75d564dbbd59cd881cf9/src/Memoization.jl#L81

but it’s not clear if they’re part of a public API, how to use them, or how they differ. The thing I’d use it for would be a to write the cache to disk (in some sense a workaround for #4), but I’m sure there are other uses.