Customized entity set with customized entity type will fail during query

[chinadragon0515]

In Api class, defined a customized entity set with customized entity type and use model extend to add the customized entity type, the query will fail.

message: "Element type cannot be found for 'PeopleWithAge'.",
type: "System.NotSupportedException",
stacktrace: "   at Microsoft.Restier.Core.ApiContextExtensions.EnsureElementType(ApiContext context, String namespaceName, String name) in D:\dev\githome\RESTier.vin\src\Microsoft.Restier.Core\ApiContextExtensions.cs:line 542
   at Microsoft.Restier.Core.ApiContextExtensions.SourceCore(ApiContext context, String namespaceName, String name, Object[] arguments) in D:\dev\githome\RESTier.vin\src\Microsoft.Restier.Core\ApiContextExtensions.cs:line 480
   at Microsoft.Restier.Core.ApiContextExtensions.GetQueryableSource(ApiContext context, String name, Object[] arguments) in D:\dev\githome\RESTier.vin\src\Microsoft.Restier.Core\ApiContextExtensions.cs:line 260
   at Microsoft.Restier.Core.ApiBaseExtensions.GetQueryableSource(ApiBase api, String name, Object[] arguments) in D:\dev\githome\RESTier.vin\src\Microsoft.Restier.Core\ApiBaseExtensions.cs:line 84
   at Microsoft.Restier.Publishers.OData.Query.RestierQueryBuilder.HandleEntitySetPathSegment(ODataPathSegment segment) in D:\dev\githome\RESTier.vin\src\Microsoft.Restier.Publishers.OData\Query\RestierQueryBuilder.cs:line 184
   at Microsoft.Restier.Publishers.OData.Query.RestierQueryBuilder.BuildQuery() in D:\dev\githome\RESTier.vin\src\Microsoft.Restier.Publishers.OData\Query\RestierQueryBuilder.cs:line 74
   at Microsoft.Restier.Publishers.OData.RestierController.GetQuery(ODataPath path) in D:\dev\githome\RESTier.vin\src\Microsoft.Restier.Publishers.OData\RestierController.cs:line 497
   at Microsoft.Restier.Publishers.OData.RestierController.<Get>d__7.MoveNext() in D:\dev\githome\RESTier.vin\src\Microsoft.Restier.Publishers.OData\RestierController.cs:line 83

[chinadragon0515]

fix merged with PR #461 ,close the issue.