Update VersionUtils to know the current version

The utils now know what the "latest" Terraria version is as of a given
build. This is used when saving, primarily, since the PLR file indicates
the current version number.
Player loader to load # of items based on version

The Player object will store as many items in a group (eg inventory) as
is supported by the current Terraria version, not the Terraria version
of the loaded PLR file.