man/*: formatting cleanup
Fix some problems with indentation (controlled by markup) and
whitespace.
- notmuch.1: reformat
Use .SS macro to make "notmuch setup" a subsection. Introduce another
subsection for the remaining commands.
- notmuch-config.1: reformat
Put all the syntax in the synopsis. Supposedly this is the the UNIX way.
- notmuch-reply.1: fix formatting issues.
Give nicer formatting for synopsis.
Insert missing SEE ALSO header.
- notmuch-dump.1: reformat using subsections
These seems more natural, although, as mentioned, it does require
referring back to the synopsis. Or maybe copying parts of the
synopsis