When installing / updating plugins, plugin data
is fetched from Spartacus first; those plugins
will habe "Spartacus" as "pluginlocation".
Later on, information about installed plugins
is fetched from cache / database, overwriting
the previously fetched data for all installed
plugins. After that, "pluginlocation" is
"local" even for plugins that live on
Spartacus if they have been installed.
So we save "pluginlocation" data to a new
"pluginsource" field before merging /
overwriting so we can detect plugins that
are available on Spartacus.
This data is present in plugins.inc.tpl
and can be used there.
Signed-off-by: Thomas Hochstein <thh@inter.net>