Rearrange protocol decoder output levels.

The protocol decoder output now varies according to --loglevel:

WARN (--loglevel 2, default):
  - show only the first annotation string, without quotes

INFO (--loglevel 3):
  - add sample numbers
  - quotes around annotation

DBG (--loglevel 4 and up):
  - add protocol decoder id
  - add annotation class
  - show all annotation strings, not just the first

In all cases, all annotation classes are shown, unless restricted with
the --protocol-decoder-annotations (-A) option.