Make the Erasmus role into a proper "school role" on the server

[Toaster192]

With erasmus people getting a 1BIT role or something right now so that they have permissions for subject channels, we should probably have the permissions under the erasmus role so it's easier to recognise and manage.

Also "fixes" #116

[Toaster192]

This means:

• adding the erasmus role override to about every subject channel
• maybe moving the erasmus role to some better place in the "role hirearchy" (via admin, not bot ig)
• moving the erasmus-incoming channel to where the rest of the "XBIT channels" are (via admin, not bot ig)
• figure out a good color for the erasmus role? (and set via admin, not bot ig)
• make sure increment_roles doesn't break whatever is then implemented
• and that role check commands support this