Admin option - Restrict magazine creation to admins/global moderators

[e-five256]

Adds a new admin panel option, disabled by default, that will restrict creation of new local magazines to admins and global moderators. Magazines added through remotes should be unaffected.

• Admin panel option
• When enabled:
• Hide option in header for regular users
• Hide option in sidebar when logged out
• Deny access to route for regular users
• Deny access in API for regular users
• Only effect local magazines

[TheVillageGuy]

I have this 'hardcoded' on my instance now, so I am in favor

[nobodyatroot]

I tested in dev with each user role using this new option both enabled and disabled, PR functions as expected. Also confirmed you're checking for apid == null in the magazine creation, so it shouldn't impact remote magazine creation.