[SAC] Trac notification defaults changed

[Sandro Santilli]

I've (hopefully) changed default trac activity notification
user preferences to NEVER notify the updater of a ticket
by mail. This was done by tweaking the [notification-subscriber]
section in `/etc/trac/trac-common.ini` and ensuring no override
existed in local environments (/var/www/trac/env/*/conf/trac.ini).

Current value of that section is:

  [notification-subscriber]
  notify_cc = CarbonCopySubscriber
  notify_owner = TicketOwnerSubscriber
  notify_previous_updater = TicketPreviousUpdatersSubscriber
  notify_reporter = TicketReporterSubscriber
  notify_updater = TicketUpdaterSubscriber
  notify_updater.adverb = never

The syntax isn't very friendly, but it looks like the user
preferences page confirms it's doing what I was after:

  https://trac.osgeo.org/geos/prefs/notification
  (you need to be logged in to see those defaults)

If anyone is against this change please raise a point now.
Rationale for the change is that the updater knows what she
did, so doens't really need a notification, and reduding
email traffic may generally help with load of TracSVN machine.

--strk;