Bug 18430 - Plugins page should have a link to viewing other types

Bug 18430 - Plugins page should have a link to viewing other types

To test:
Go to the plugins page from
Reports->Report plugins
Tools->Tool plugins
Admin->Manage plugins

Ensure that you have a 'View plugins by class button'

Ensure the button does what you would expect

Signed-off-by: Christopher Brannon <cbrannon@cdalibrary.org>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>