Bug 9731 - Remove changelanguage.pl in favor of opac-changelanguage.pl

Bug 9731 - Remove changelanguage.pl in favor of opac-changelanguage.pl

Remove that file that duplicates the behaviour of the correct
opac-changelanguage.pl file and fix references to it in the templates.

To test:
- Apply the patch
- Choose a different language in the OPAC
- It should work as expected.

To+

Sponsored-by: Universidad Nacional de Cordoba
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Tested again at RM's request

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>