Introduce db cache

OsmAnd/src/net/osmand/plus/exploreplaces/ExplorePlacesProviderJava.java

@@ -32,6 +32,12 @@
 // TODO remove checks poi type subtype null
 // TODO display all data downloaded even if maps are not loaded
 // TODO: why recreate provider when new points are loaded? that causes blinking
+// TODO: scheduleImageRefreshes in layer is incorrect it starts downloading all images and stops interacting
+//.      images for download should be correctly calculated before schedule based on overlap
+// TODO images shouldn't be queried if they are not visible in all lists! size doesn't matter !
+// TODO show on map close button is not visible
+// TODO layer sometimes becomes non-interactive - MAP FPS drops
+// TODO Context menu doesn't work correctly and duplicates actual POI  
 // Extra: display new categories from web
 public class ExplorePlacesProviderJava implements ExplorePlacesProvider {