Fixes DynamicNode issue not implementing IEnumerable<DynamicNode>

Adds a few unit tests for DynamicDocument/DynamicNode and fixes both to properly support the 'Take' method
as this wasn't really working. Not sure how or why it was working previously. Have also allowed for extension
methods to be executed against either of these objects that accept IQueryable which was not supported before.

src/Umbraco.Web/Mvc/RenderViewPage.cs

@@ -52,6 +52,12 @@ namespace Umbraco.Web.Mvc
 		public dynamic CurrentPage { get; private set; }
 
 		private ICultureDictionary _cultureDictionary;
+
+		/// <summary>
+		/// Returns the dictionary value for the key specified
+		/// </summary>
+		/// <param name="key"></param>
+		/// <returns></returns>
 		public string GetDictionaryValue(string key)
 		{
 			if (_cultureDictionary == null)