Add "safety compilation". Improved, fixed messages

- node ext searcher also looks for "iojs" if no node(js?) found.
- koch ensures the local work dir compiler is freshly compiled before executing the tests.
- the tester can only run in the repo dir - now the compiler and libs used are also explicitly the local dirs - so no confusion from system wide pathing ("sufficiently sandboxed").
- fixed expectations in tmitems.nim test to match changes in json mod.
- re-layouted the columns / row printing slightly, making test fails pop out more, and everything "normal" layed back.

tests/stdlib/tmitems.nim

@@ -11,8 +11,8 @@ fpqeew
 [11, 12, 13]
 [11, 12, 13]
 [11, 12, 13]
-{"key1": 11, "key2": 12, "key3": 13}
-[11, 12, 13]
+{"key1":11,"key2":12,"key3":13}
+[11,12,13]
 <Students>
   <Student Name="Aprilfoo" />
   <Student Name="bar" />