fix for #9 - support for #load to load dependent scripts (clean)

Example use:

         //script1
                #load "script2.csx"
                using System;
                using System.Collections;

                Console.WriteLine("Hello Script 1");

         //script2
                using System;
                using System.Core;

                Console.WriteLine("Hello Script 2");
Will produce:

                using System;
                using System.Core;
                using System.Collections;

                Console.WriteLine("Hello Script 2");
                Console.WriteLine("Hello Script 1");

Also supports:
 - being called inline (not just on top of the file).
 - absolute script paths (although am not sure about that)