adjust max_size / max_count before beta release

[ThomasWaldmann]

the small packs are good for testing, but people will try the beta with lots of data, so we should use a resonable size/count for the release.

[ThomasWaldmann]

Guess max_size=50000000 (50MB) is a good start.

Do we have good reasons to not use max_count=None?

[ThomasWaldmann]

We could even permanently have the more practical value and only set the low value for testing (like we also reduce the KDF rounds only for testing).

@mr-raj12 ^