bug 3049: display correct due date of renewed loans

bug 3049: display correct due date of renewed loans

The intranet item display provided by moredetail.pl
would display the original due date of the item, and
would thus be incorrect if the item had been renewed
and got a different due date.

The incorrect date was coming from items.onloan,
which AddIssue() sets to the due date.  This patch
fixes the bug in two ways:

[1] AddRenewal() now updates items.onloan with the
    correct due date.
[2] Two templates were updated to display the
    due date from (indirectly) issues.date_due
    instead of items.onloan, thus making it less
    likely that the wrong value will be displayed.

This patch does *not* update items.onloan to reflect
the correct due date.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>