Bluemap Player Visibility

• Added command set, e.g /bmpv <status>
• Added persistent storage of configuration in config/hide-players-bluemap.json

Command set:

Command	Usage	Requires OP
/bmpv default <status>	Used to change status for all new players	Yes
/bmpv show <user>	Used to show a specific user on the Bluemap	Only if specifiying a user that is not you
/bmpv hide <user>	Used to hide a specific user on the Bluemap	Only if specifying a user that is not you

NOTE: /bmpv show <user> doesn't require a user if it is acting upon yourself