Decouple "admin" and "mod" roles

[auryn-macmillan]

Currently, snapshot admins are able to both edit the space settings and moderate proposals.

As part of GIP-77, we would like to add a new "moderator" role to decouple the moderator permissions from the admin role.

The desired role structure looks as follows:

• Admin: able to edit the space settings.
• Moderator: able to moderate proposals.
• Author: able to create proposals without constraints.
• Everyone: able to vote in proposals and able create proposals if they pass validation.

This issue should be implemented via a PR to the snapshot codebase, including updates to their documentation.

[zzuziak]

Hey @auryn-macmillan, let us know your thoughts on the solution from the above PR. You can have a look at it live here: https://snapshot.org/#/gnosis.eth/settings

[auryn-macmillan]

Looks awesome! I had a play with it earlier and it seems to do what we need. Appreciate the support on this.