Bug 10796: Use $category->effective_change_password in the OPAC

Bug 10796: Use $category->effective_change_password in the OPAC

This patch makes the OPAC pages that rely on OpacPasswordChange use the
current patron's category to make the decision to allow password change
or not.

It does so by making sure all the places in which OpacPasswordChange was
used, use $logged_in_user->category->effective_change_password instead.

Special attention is required on the case of opac-registration-verify.pl
in which the use of an unblessed Koha::Patron object is changed in
favour of the blessed object, so we can actually use the new method to
make a decision on the text to display.

To test:
- Go through the OPAC pages, check that the password change strings and
links are displayed only whne appropriate.
- Sign off :-D

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>