Nameaserver: allow emphasizing name candidate

Server names can now be suggested by either making the entire comment
the suggestion, or the first bold/italic item in the comment (that is
actually a valid server name) will be taken instead.
Nameaserver: don't use contest mode

Contest mode being active was also being used as an indicator of which
thread was the currently active one, so this includes some changes to
use an empty server_names attr as that indicator instead.
Nameaserver: update selftext when activating name
Debug footer: link server name to source comment
temporary transition code to handle non-json