implement new django-based models and loadmappkg command

src/c3nav/mapdata/apps.py

@@ -1,25 +0,0 @@
-from django.apps import AppConfig
-from django.conf import settings
-from django.core.checks import Warning, register
-
-from . import mapmanager
-
-
-@register()
-def has_map_data_check(app_configs, **kwargs):
-    if not settings.MAP_DIRS:
-        return [Warning(
-            'There are no map data directories configured.',
-            hint='Add mapdirs=/path/to/directory to your c3nav.cfg.',
-            id='mapdata.W001',
-        )]
-    return []
-
-
-class MapdataConfig(AppConfig):
-    name = 'c3nav.mapdata'
-    verbose_name = 'map data manager'
-
-    def ready(self):
-        for map_dir in settings.MAP_DIRS:
-            mapmanager.add_map_dir(map_dir)