Bug 21890: Allow restricting password resets by patron category

Bug 21890: Allow restricting password resets by patron category

This patch makes the templates relying on the OpacResetPassword syspref
use the introduced TT plugin method instead by changing:

[% IF Koha.Preference('OpacResetPassword') %]

=>

[% IF Categories.can_any_reset_password %]

To test:
- Verify that all the places in which the 'forgot password' link is
displayed in OPAC keep working, provided there's at least one category
that has the flag set
- Attempt to recover the password for a patron that belong to a valid
category (i.e. that has the flag set)
=> SUCCESS: You can go through the normal process
- Attempt to recover the password for a patron that belongs to a
category with the flag unset.
=> SUCCESS: Once Koha identifies your category, you are told you are not
allowed to do it
- 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>