feat(maps_utils,district): Use FeatureCollection GeoJSON type by default

- All features in GeoFeatureDetailPage will be converted to FeatureCollection
- Each collection may have multiple GeoJSON feature objects, each with
  its own properties. This enables us to provide customized title & description
  for individual features. You can set 'title' and 'description'
  properties and they will be used both in map and on detail page.
- Each FeatureCollection sits on its own Leaflet layer.
- Having each FeatureCollection on own layer enabled us to do precise
  muting support: layer will be completely removed/added which greatly
  helps to avoid visual clutter.
- Muting support added to whole geo categories as well!
- Fixed map collection block.