Fix 0013816: Update history when copying issues

Until now, copying bugs using the "View Issues" page creates wrong/
incomplete history (entries for notes reflect the id's of the original
issue's notes) and also does not record any trace that the new issue is
in fact clone of another, which can be a source of confusion.

This commit prevents the duplication of the original bug's history,
generating instead a single history entry similar to what happens when
cloning a bug with the Clone button in view.php page.

The display of history entries for cloned bugs has been slightly
modified, the bug id is now printed under the 'Field' column instead of
the 'Change' column, like entries for adding notes (as cloning s not a
change).