Address reviews

- Replacing `BaseData.AdjustResolution` for `DefaultResolution` and
`SupportedResolutions`
- Making `Resolution` nullable for `Algorithm.AddData` methods
- The `ISubscriptionDataConfigService` will set the default resolution
if none was provided and assert it is supported
- Fix bug with `PythonData` `IsSparseData` and `RequiresMapping`
resolution

Algorithm.CSharp/CustomDataUsingMapFileRegressionAlgorithm.cs

@@ -47,13 +47,13 @@ namespace QuantConnect.Algorithm.CSharp
             SetEndDate(2013, 07, 02);
 
             var foxa = QuantConnect.Symbol.Create("FOXA", SecurityType.Equity, Market.USA);
-            _symbol = AddData<CustomDataUsingMapping>(foxa, Resolution.Tick).Symbol;
+            _symbol = AddData<CustomDataUsingMapping>(foxa).Symbol;
 
             foreach (var config in SubscriptionManager.SubscriptionDataConfigService.GetSubscriptionDataConfigs(_symbol))
             {
                 if (config.Resolution != Resolution.Minute)
                 {
-                    throw new Exception("Expected resolution to be adjust to Minute");
+                    throw new Exception("Expected resolution to be set to Minute");
                 }
             }
         }
@@ -78,7 +78,7 @@ namespace QuantConnect.Algorithm.CSharp
 
                     _initialMapping = true;
                 }
-                else if(Time.Date == new DateTime(2013, 06, 29))
+                else if (Time.Date == new DateTime(2013, 06, 29))
                 {
                     if (mappingEvent.NewSymbol != "FOXA"
                         || mappingEvent.OldSymbol != "NWSA")
@@ -173,10 +173,25 @@ namespace QuantConnect.Algorithm.CSharp
                 return ParseEquity(config, line, date);
             }
 
-            public override Resolution AdjustResolution(Resolution resolution)
+            /// <summary>
+            /// Gets the default resolution for this data and security type
+            /// </summary>
+            /// <remarks>This is a method and not a property so that python
+            /// custom data types can override it</remarks>
+            public override Resolution DefaultResolution()
             {
                 return Resolution.Minute;
             }
+
+            /// <summary>
+            /// Gets the supported resolution for this data and security type
+            /// </summary>
+            /// <remarks>This is a method and not a property so that python
+            /// custom data types can override it</remarks>
+            public override List<Resolution> SupportedResolutions()
+            {
+                return new List<Resolution> { Resolution.Minute };
+            }
         }
     }
 }