Text output by a hosted message may not be in UTF8. This is not the case
for TakTuk or our controlled programs. Callback from isengard now send
the content of the gathered output in binary and utf8 form.
When the output of a subprocess is gathered for the root node, it is
encoded in bas64. On the root, the user should take care of the final
encoding. The Executor task is now able to deal with other encoding than
UTF-8.