Use API to play sound. (Should work identically)

This should result in an identical packet, except that the 4th one might
be a 7 or a 0 (bedrock/air).
Remove more NMS usage: make InvManager save a list

ConfigurationSections handle lists of ConfigurationSerializable objects
quite nicely. No need to turn a NBT stream into base64 and save that as a
string.