Use /usr/bin/env ksh for portability
Allow path to pfexec to be specified as a configuration option

OSes which don't have pfexec (namely FreeBSD) can use sudo instead.
Include verbose switch in debug log message
support for a local mode when REMHOST=localhost

In this mode, ssh is bypassed, and $REMUSER and $REMZFS are ignored.
don't leave PID file when aborting for no sources
abort when no matching local snapshots found
Merge branch 'pvalkone-freebsd-portability-fixes'

Closes #4.
Resolved Conflicts:
	zfs-backup.sh