Made it so Client.EnsureColumns can take an ICollection, isntead of IList

InABox.Core/Client/Client.cs

@@ -83,7 +83,7 @@ namespace InABox.Clients
                 row?.FillObject(entity);
             }
         }
-        public static void EnsureColumns<TEntity>(IList<TEntity> entities, Columns<TEntity> columns)
+        public static void EnsureColumns<TEntity>(ICollection<TEntity> entities, Columns<TEntity> columns)
             where TEntity : Entity, IRemotable, IPersistent, new()
         {
             var newColumns = Columns.None<TEntity>()