Set the default of MaxTop to null

Author: xuzhg

src/Microsoft.AspNet.OData.Shared/Query/DefaultQuerySettings.cs

@@ -10,7 +10,7 @@ namespace Microsoft.AspNet.OData.Query
     /// </summary>
     public class DefaultQuerySettings
     {
-        private int? _maxTop = 0;
+        private int? _maxTop;
 
         /// <summary>
         /// Gets or sets a value indicating whether navigation property can be expanded.

src/Microsoft.AspNet.OData.Shared/Query/ModelBoundQuerySettings.cs

@@ -12,16 +12,13 @@ namespace Microsoft.AspNet.OData.Query
     public class ModelBoundQuerySettings
     {
         private int? _pageSize;
-        private int? _maxTop = 0;
+        private int? _maxTop;
         private Dictionary<string, ExpandConfiguration> _expandConfigurations = new Dictionary<string, ExpandConfiguration>();
         private Dictionary<string, SelectExpandType> _selectConfigurations = new Dictionary<string, SelectExpandType>();
         private Dictionary<string, bool> _orderByConfigurations = new Dictionary<string, bool>();
         private Dictionary<string, bool> _filterConfigurations = new Dictionary<string, bool>();
 
-        internal static ModelBoundQuerySettings DefaultModelBoundQuerySettings = new ModelBoundQuerySettings
-        {
-            _maxTop = 0
-        };
+        internal static ModelBoundQuerySettings DefaultModelBoundQuerySettings = new ModelBoundQuerySettings();
 
         /// <summary>
         /// Instantiates a new instance of the <see cref="ModelBoundQuerySettings"/> class