UserBinary type1-5 and EnhancedMinidata are transient session state
resent by the client on every login. Persisting them to the DB on
every set was unnecessary I/O. Both are now served exclusively from
server-scoped in-memory maps (userBinaryParts, minidataParts).
Includes a schema migration to drop the now-unused type2/type3
columns from user_binary and minidata column from characters.
Ref #158
