find and eliminate 16-bit color depth wm_jp2s

(for further explanation, see separate bug report on enabling luratech and grayscale modules to handle these images more gracefully - https://bugs.launchpad.net/deriver/+bug/174324)

Find the 4000-5000 such items, delete the bad wm_jp2s, and rederive so that pdfs become compressed and grayscale module can run.

If anyone else gets to this before me, in ~/hank/wm16/ are lists of items produced during the key period that Tracey helped me compile. The bad ones can be identified by the ratio of pdf size to # pages, or by executing something like

unzip -p laubergedelangeg00sguoft_wm_jp2.zip laubergedelangeg00sguoft_wm_jp2/laubergedelangeg00sguoft_wm_0000.jp2 | identify -format "%z" -
(the result will be 8 or 16)