Allow opt-out of gms related memos

[mistohise]

As it says on the tin, please allow the sending of memos for GMS activity to be opt-out-able.

Note: this is not the same as setting "nomemo" or whatever to turn off all memos.

[mniip]

Does /msg MemoServ IGNORE ADD <master gms account> not cut it?

[mistohise]

Don't know tbh. But really, it shouldn't have to work that way. Referencing this back to another issue, where you raised the point about unnecessary work being done, it's daft to have a thing trying to send memos that people don't want.

[decontamin4t0R]

This could be awesome for v2 with the issue to send e-mails.