Update QueryableExtensions.cs

QueryableExtensions now handle OrderBy and ThenBy on child collections.
Update QueryableExtensions.cs

Removed restriction to OrderBy/ThenBy. We can infer the child type from the return type of any MethodCallExpression - OrderBy/ThenBy aren't the only methods that can be converted to SQL. The caller might be using SqlFunctions, or even EdmFunctionAttribute.
Merge branch 'develop' of github.com:iaingalloway/AutoMapper into iaingalloway-develop