Move ground plane grid settings into database and allow user to set them

docker-compose.example.yml

@@ -10,7 +10,6 @@ services:
     environment:
       DATABASE_URL: postgresql://van_dam:password@db/van_dam?pool=5
       SECRET_KEY_BASE: a_nice_long_random_string
-      GRID_SIZE: 260
       # RAILS_RELATIVE_URL_ROOT: /vandam Sets the root of the app to /vandam useful for reverse proxies with nginx
     depends_on:
       - db
@@ -31,4 +30,3 @@ services:
 
 volumes:
   db_data:
-