Add commands to transfer and wipe player data

[123Veasper]

Yo, I'm really missing the following commands:

1. /playerdata export <1nick> <2nick> - Export absolutely all data about a player (statistics, achievements, etc.) from 1nick to 2nick.

2. /playerdata clear - Completely delete all data about a player (statistics, achievements, etc.).

Right now, none of this exists. Having to manually go into advancements and playerdata to remove the player is one thing, but what if I have 5 servers? On top of that, I also need to delete the player's data from MySQL and Redis...