Multisite: Delete settings should be Super Admin only and global

Hi, Thanks for the great plugin.

A small suggestion.
I think that in a WordPress Multisite installation, the following options, now available to all subsites admins under the “Series->Settings” Advanced tab, should be available only to the Super Admin and should be global, and  storing it via get_site_option() / update_site_option()

• Series Categories — Delete all “Series Categories” data from the database when deleting the plugin.
• Series Settings — Delete all PublishPress Series data from the database when deleting the plugin.

Bests,
Lena