Essential-Commands

dde547c1 - [on 1.18] Allow nickname to be set by command blocks...

[on 1.18] Allow nickname to be set by command blocks... This includes some breaking permissions changes: - By default, using **Placeholders** in nicknames requires an OP level of 2 (from 4) - By default, using **entity selectors** in nicknames requires an OP level of 2 (from 4) NOT INCLUDED FROM CHERRY-PICK Add `FeedbackReceiver`, `IFeedbackReceiver`, which `PlayerData` implements, to allow easily implementing commands for us by players _or_ command blocks. (PLAYERDATA DOES NOT IMPLEMENT IN THIS CHERRY-PICK)