Initial skeleton work of periodic on disk caching

AS1024.GeoFeed/GeoFeedBuilder/GeoFeedCacheService.cs

@@ -0,0 +1,26 @@
+
+using System.ComponentModel.DataAnnotations;
+using AS1024.GeoFeed.Models;
+using Microsoft.EntityFrameworkCore;
+
+public class GeoFeedCacheService : IHostedService
+{
+    public Task StartAsync(CancellationToken cancellationToken)
+    {
+        throw new NotImplementedException();
+    }
+
+    public Task StopAsync(CancellationToken cancellationToken)
+    {
+        throw new NotImplementedException();
+    }
+}
+
+public class GeoFeedCacheEntry : IPGeoFeed {
+    [Key]
+    public int Id { get; set; }
+}
+
+public class GeoFeedCacheDbContext : DbContext {
+    public virtual DbSet<GeoFeedCacheEntry> GeoFeedCacheEntries {get;set;}
+}