Pretty printers

Hi,
  Until now, pretty printers have been working from the console window
only. I just pushed a commit at https://github.com/monnerat/insight that
implements them in local variables and watch windows too.

One remaining problem: the displayed items do not change format when the
pretty printers are enabled/disabled from the console window: you have
to close and reopen window(s) to make the change effective, or step an
instruction.
Changing the displayed item formats at pretty-printer enable/disable
time would require to trap the command and I did not yet find how to do
it... Patches are welcome :-)

Cheers,
Patrick