Convert old line-cutter procedure to Markdown

[Joedang]

This thing is in a pretty obscure location for mission-critical information. It needs to be converted to Markdown and added to this repo. @andrewgreenberg, can we get the source for that? (That would be nicer than grinding it through Pandoc.)

[andrewgreenberg]

Done! I'm assigning it back to you for further cleanup, but I converted the AVIs to MP4s because 2018 and cleaned up a few other things.. links are probably borked and other things, but at least it's there now!

https://github.com/psas/lv3.0-recovery/tree/master/LV2c_Line_Cutters