Bug 17935: Follow up for C4::Plugin...

Bug 17935: Follow up for C4::Plugin...

TEST PLAN
---------
-- apply first patch
git grep "C4::Plugin"
-- still two references
perldoc Koha::Plugins::Base
perldoc Koha::Plugins::Handler

-- apply this patch
git grep "C4::Plugin"
-- no references
perldoc Koha::Plugins::Base
perldoc Koha::Plugins::Handler
-- should look fixed

 Please enter the commit message for your changes. Lines starting

Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>