Add manual page generation for the qmp-shell and qmp-shell-wrap tools. Downstream packaging guidelines ask for manpages for command line scripts, so let's oblige.
Sample HTML generation can be seen at e.g. https://jsnow.gitlab.io/python-qemu-qmp/qmp_shell.html
manual pages need to be built manually after checkout with
make -C docs man
Closes #28 (closed)