Bug 10942: (follow-up) make AUTOMATIC_TRANSLATIONS_UPDATE default to yes

Bug 10942: (follow-up) make AUTOMATIC_TRANSLATIONS_UPDATE default to yes

This patch makes AUTOMATIC_TRANSLATIONS_UPDATE default to yes,
meaning that package upgrades will update the translations by
default.  This seems definitely sensible for new installations,
but as there are some older installations that may be in the
habit directly editing generated translated templates, it's
less clear whether this is a good idea for upgrades.

This patch is intentionally separate, and can be ignored if
the consensus swings towards having AUTOMATIC_TRANSLATIONS_UPDATE
be off even for new installations or if somebody counter-patches
with adding debconf support.

To test:

- As with the previous patches in the series, except that the
  translations would be automatically updated upon installing
  the new package.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Robin Sheat <robin@catalyst.net.nz>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>