Migrate from MessagePack to MemoryPack

[mrdav30]

There is a new library that supersedes MessagePack (MemoryPack). It has many advantages over MessagePack. Migration is as simple as replacing the tags and adding the partial keyword to the serialized classes. Would probably be worth invstigating if migrating to MemoryPack is an option. It is faster and has a lot less limitations.

Originally posted by @SPapandreou in #37