Refresh maps list in New game window #74

Currently maps in the maps list are loaded only when UI is initialized, so when installing new maps in runtime, you need to restart the client

Propsal

Ideally, it would be great to run filesystem watcher, which would monitor the addition/deletion of files from the maps/ directory so that the interface is always in sync, but it could be tricky to implement. One of the simplest options is to call LoadMaps when opening the window