Refactoring: More reasonable handler logic and naming introduced.
Implemented GameOver logic.
Implemented NewTable logic.
Implemented Table abandoned logic.
Changed TableList packet's Table id from 'id' to 'table_id'.
Added packet constant: MSG_TABLE_CLOSED.
Renamed function sendPacketToPlayers to sendPacketToAll.
Refactor of SitDownHandler: moved sitDown logic into AbstractPacketHandler.
Fixed type hint in comment.