Add ability for magazine ownership to be transferred to another moderator

[AndrewMathis13]

Is your feature request related to a problem? Please describe.
Currently there is no user-facing option to transfer the ownership of a magazine to another account. Whether the current owner is moving to a new account, no longer wants to participate in the moderation of a particular magazine, or just isn't able to be as active in the magazine anymore, there isn't an option to transfer the magazine to another account or step away without just abandoning the magazine.

Describe the solution you'd like
It would be nice if there was a settings option in the magazine panel that would allow the magazine owner to transfer ownership of the magazine to one of the other moderators.

Describe alternatives you've considered
The only other alternative currently is to reach out to your server admin and ask them to manually transfer the ownership of the magazine, but it would be nice if there was a setting built specifically for this that any user could easily use on their own.

[BentiGorlich]

Related #600 - not the same though

[BentiGorlich]

The only limitation would be that the new owner has to be on the same instance as the magazine. Otherwise this should be fairly easy to implement :)