Delete unused code for fragmented SERVACKs

If we ever get around to modifying libzephyr here, the code's still in version
control.
Improve the display on received notices

The various ACKs get really confusing. Also display whether we think a message
is authentic.
Save keys in our subscription notices

Requires further unmerged changes to libzephyr.
Punt ZSubscribeTo wrapper

Still in version control if we need it. Seem to have settled on implementing it
in user code.
Refactor object-to-notice conversion into a separate function

Not that it wasn't separate before. But now it's separate without explicitly
freeing data. So yay.
Comment was wrong
Expose ZFormatNotice
Tidy up test code some more

Remove unnecessary console.dir at the start. Also register the notice listener
earlier, so I can see the subscription SERVACKs.
Properly fragment subscription notices

Never break them at subscription boundaries.
Appease the licensing gods

I suppose it's good to have one of those things.