Convert "outgoing" literals to unicode

The patch convers most literals throughout marconi to unicode. Lietrals
not leaving "marconi-land" were left untouched.

This is the first patch of a serie that will enforce unicode usage
within marconi. Decode early, encode late.

String format parameters were left untouched on purpose. Those
parameters should be decoded before getting there.

Implements blueprint enforce-decoding

Change-Id: I85e534ced188191c9c7a17e9908cb720e7d63ca9