Bug 16270 (followup) Typo authentification vs authentication

Bug 16270 (followup) Typo authentification vs authentication

Additionally fix typo in following files:
koha-tmpl/intranet-tmpl/prog/en/modules/admin/preferences/opac.pref
koha-tmpl/opac-tmpl/bootstrap/en/modules/errors/errorpage.tt

To test: Apply patch, verify in files that authentification is
         replaced by authentication

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>