added argument checking to append (#549)
added argument checking to append (#549)

It aborts if an unknown filter is used. If the final
argument in not a "wc" argument, checks to make sure there is
not a "|" in the name, which would suggest a typo.
Allows both 'grep -iw' and 'grep -wi'.
OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ,OpenVnmrJ/OpenVnmrJ