Improve horse registration UX

[Nevakanezah]

Horses are currently registered in a fairly robust way, with redundant registration checks at spawn, taming, and inspection. While registration is important to our workflow, it's also an area that's poorly communicated to players for the following reasons:

• No messages are shown to players when a horse is registered
• The inspector module is the only means for non-op players to verify the registration status of a horse
• The purpose and functionality of registration is poorly communicated to players, as player-facing information prefers the language of "Wild" vs "Tamed".
• A corner case exists when the plugin is installed on an existing map with the inspector disabled - The inspector is the only means of registering horses (violently, at that), but players receive no feedback as to what has happened and why. This also causes inconsistency in horse behavior, as registered horses follow gender/relatedness rules while unregistered ones do not.

Improve the horse registration user experience such that players are given an appropriate amount of information about horse registration events, and which horses are registered.

[Nevakanezah]

Alternate options include:

• Registration checks on mounting / feeding
• A server-wide sweep for tamed, unregistered horses to have them all registered immediately. This could be enacted via config (ie: "scan-on-startup"), or via admin command.