New Commands: SET_PLAYER_WEATHER & SET_PLAYER_TIME

Two new player commands for client-side weather and time control:

SET_PLAYER_WEATHER -- Set weather per-player without affecting the server or other players.
SET_PLAYER_WEATHER weather:CLEAR # clear skies
SET_PLAYER_WEATHER weather OWNFALL # rain/storm
SET_PLAYER_WEATHER weather:RESET # restore server weather

SET_PLAYER_TIME -- Set time per-player, with optional relative mode.
SET_PLAYER_TIME time:6000 # noon
SET_PLAYER_TIME time:18000 relative:true # offset from server time
SET_PLAYER_TIME time:-1 # reset to server time

Common time values: 0 sunrise, 6000 noon, 12000 sunset, 18000 midnight.