Update hack/make/ubuntu to use the new markdown-based manpages

This also removes all the old man pages, .gitignores their directory, and updates the md2man-all.sh script to be easier to read and more friendly to being called within hack/make/ubuntu.

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #2 from tianon/generate-manpages-make-ubuntu

Update hack/make/ubuntu to use the new markdown-based manpages