Fix hyphens vs. minus signs, whatis entry, and improve formatting of man page

As promised earlier today. This enhances formatting a bit here and there, and fixes errors relating to the use of hyphens as minus signs [1] and a missing "\-" in the name section [2].

[1] http://lintian.debian.org/tags/hyphen-used-as-minus-sign.html
[2] http://lintian.debian.org/tags/manpage-has-bad-whatis-entry.html


Eventually, it would be best to incorporate most of the information in the README into the man page, especially usage examples, impact of various options and choices etc, but that's a separate issue of course. If only there'd be 25 hours in a day...