Adds tostring and type functions

Upsilon/BaseTypes/ScriptIterator.cs

@@ -46,7 +46,7 @@ namespace Upsilon.BaseTypes
                 while (baseEnumerator.MoveNext())
                 {
                     var key = baseEnumerator.Current;
-                    if (key.Type == Type.Nil)
+                    if (key == null || key.Type == Type.Nil)
                         break;
                     var value = BaseIterator.GetValueFromIndex(key);
                     if (value.Type == Type.Nil)

Upsilon/StandardLibraries/BasicFunctions.cs

@@ -37,7 +37,6 @@ namespace Upsilon.StandardLibraries
             return new PairsScriptIterator(table);
         }
 
-
         [StandardLibraryScriptFunction("tonumber")]
         public ScriptNumber ToNumber(ScriptString obj)
         {
@@ -51,5 +50,18 @@ namespace Upsilon.StandardLibraries
                 return new ScriptNumberLong(long.Parse(str));
             }
         }
+
+        [StandardLibraryScriptFunction("tostring")]
+        public ScriptString ToString(ScriptType obj)
+        {
+            return new ScriptString(obj.ToString());
+        }
+
+        [StandardLibraryScriptFunction("type")]
+        public ScriptString Type(ScriptType obj)
+        {
+            return new ScriptString(obj.Type.ToString());
+        }
+
     }
 }