Bug 16586: Koha Plugins: Limit results of GetPlugins by metadata

Bug 16586: Koha Plugins: Limit results of GetPlugins by metadata

It would be helpful if we could find a plugin based on some metadata
tag as returned by the plugin. This extends the use of GetPlugins that
already supports searching on method.

GetPlugins is used in: admin/edi_accounts.pl, plugins/plugins-home.pl and
tools/stage-marc-import.pl. The changes in these three scripts are
minimal and just related to parameter passing.

Test t/db_dependent/Plugins.t includes another test for GetPlugins. In this
regard a metadata tag has been added to t/Koha/Plugins/Test.pm.

NOTE: This adjustment will also be used in a redesign for bug 15545.

Test plan:
Run t/db_dependent/Plugins.t.
Enable pref UseKohaPlugins and config var enable_plugins.
Go to plugins-home.pl. Verify that it still lists your plugins.
Bonus: Check edi_accounts or stage-marc-import.pl if you have a working
plugin for that.

Signed-off-by: Liz Rea <liz@catalyst.net.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>