Added .betstats command, shows statistics for multiple gambling commands, .slotstats removed as it is obsolete

src/NadekoBot/Db/NadekoContext.cs

@@ -472,6 +472,14 @@ public abstract class NadekoContext : DbContext
             .IsUnique());
 
         #endregion
+        
+        #region GamblingStats
+
+        modelBuilder.Entity<GamblingStats>(gs => gs
+            .HasIndex(x => x.Feature)
+            .IsUnique());
+
+        #endregion
     }
 
 #if DEBUG