Since the pack type was stored in 4 bits, only 15 values were allowed (0 was reserved).
Allow virtually unlimited types by storing type info in a base-128 encoded integer following the tag when the type bits in the tag are set to 0xF.
Also separate the type IDs used in the pack (PackTypeMap) from those presented to the user (PackType). The prior PackType enum exposed implementation details to the user, e.g. pckTypeUnknown.
The help data can be represented more compactly in a pack and this separates data needed for help from data needed for parsing, freeing each to have a more appropriate representation.
