MapMarkers

Improvements were applied to reduce impact on the world thread, especially in the marker creation and removal routines. The mod no longer rebuilds all markers on every simple operation, and saving markers.db was moved outside world.execute(...), reducing the chance of server performance warnings.
The plugin compatibility metadata was also corrected. The manifest.json now uses ServerVersion: "*", aligning the mod with the pattern observed in HytaleServer.jar and preventing target server version warnings for MapMerker. The final build was compiled successfully, and the new MapMerker.jar is ready to replace the old version on the server.