ExpandoObjectConverter supports emitting an Array type

Modify ExpandoObjectConverter.cs to support emitting an Array type instead of an IList<object> type when processing a JSON array and the UseArrayTypeForCollections property is true.

Added test to validate that the ExpandoObjectConverter is generating an Array instead of an IList<object> when the UseArrayTypeForCollections property is true.

Refers to this issue on json.CodePlex.com: http://json.codeplex.com/workitem/22878