make constructors for SpaceSaver subclasses public so that deserializers that are not in this package have access to them
use different public apply method instead of public constructor for SSMany
Revert "use different public apply method instead of public constructor for SSMany"
After discussion with ianoc we decided to also serialize bucketsOption which requires the main constructor of SSMany to be public.
This reverts commit bda78370ea701451765d4fe821fa87969ae3198c.
Merge pull request #289 from tresata/feature/spacesaver-fix

make constructors for SpaceSaver subclasses public so that deserializers...