New port: sysutils/wmscript: System monitoring dockapp for Window Maker

WMScript allows to specify a command and have the numeric result
of that command displayed in the dock app's window. Up to 5 things
to monitor, the interval is configurable.

See http://freshmeat.sourceforge.net/projects/wmscript for details.

PR: 253346
Submitted by: Igor Pokrovsky <ip@unixway.org> (maintainer)
Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D28558