new port: sysutils/gsh

The gsh program is a command line program used to run commands on multiple remote host computers in parallel. The gsh program has few dependencies, requiring Perl and the OpenSSH client software to work.

PR: 210755
Submitted by: jsmith@resonatingmedia.com
Reviewed by: matthew
Approved by: matthew (mentor)
Differential Revision: https://reviews.freebsd.org/D9002