Use $(wildcard ...) to generate the list of man pages based on the rst
source files present in the man page directories, instead of reading
conf.py. This has three main benefits:
1) This makes the man page build slightly less complicated and easier
to understand. At least there are fewer moving parts.
2) This makes the build fail if we add a man page rst file, but fail
to add it to conf.py.
3) We can use Sphinx constructs in conf.py that are not available when
importing the file into a normal python program such as
mkdocdeps.py.
This is the output from sphinx-quickstart, massaged a bit, along with
our existing man pages converted to rst.
A skeleton notmuch-emacs manual is also included. It is not suitable
for end user use yet.
