Support multiple counselor adding policies

[arades79]

Not every server will have the same use case. It is plausible some servers will be loosely administrated, and open to allowing anyone to be a counselor, where some groups would want thorough vetting of all counselors, and need to add them only manually through administration. These could easily be controlled with settings inside the server that communicate the policy to connecting clients, and then depending on the connected server's policy, a user could sign up as a counselor for that server from within the application, be provided an administrator email to request access, and possibly other policies.