Player data to Database (#5475)

* Player data to Database

Add player data into databases (SQLite3 & PG only)

PostgreSQL & SQLite: better POO Design for databases

Add --migrate-players argument to server + deprecation warning

* Remove players directory if empty

src/CMakeLists.txt

@@ -377,6 +377,7 @@ set(common_SRCS
 	convert_json.cpp
 	craftdef.cpp
 	database-dummy.cpp
+	database-files.cpp
 	database-leveldb.cpp
 	database-postgresql.cpp
 	database-redis.cpp