[messages] add INFO_MSG and print it to GCS console

Uses a separate string_of_chars function for now to convert the
char array from ivy (e.g. |i,n,f,o, ,m,s,g|) to normal string to
nicely write to console and messages app.

Proper solution would be to write char arrays as normal "quoted string" to the ivy bus.
[JTAG][BMP] latest blackmagic firmware easy to update from within paparazzi: closes #871