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.