Add new port: security/teleport

Gravitational Teleport ("Teleport") is a modern SSH server for remotely
accessing clusters of FreeBSD or Linux servers via SSH or HTTPS. It is
intended to be used instead of sshd. Teleport enables teams to easily
adopt the best SSH practices like:

• Integrated SSH credentials with your organization Google Apps identities or other OAuth identitiy providers.
• Teleport uses certificate-based access with automatic expiration time
• Enforcement of 2nd factor authentication
• Cluster introspection: every Teleport node becomes a part of a cluster and is visible on the Web UI
• Record and replay SSH sessions for knowledge sharing and auditing purposes
• Collaboratively troubleshoot issues through session sharing
• Connect to clusters located behind firewalls without direct Internet access via SSH bastions

Teleport is built on top of the high-quality Golang SSH implementation
and it is compatible with OpenSSH.

Initially submitted by: staticwizard@hotmail.com in ports/219332

PR: ports/219332
Approved by: swills (mentor)
Reviewed by: yuri, swills, pi
Differential Revision: https://reviews.freebsd.org/D14576