Documentation/binfmt_misc.txt: convert it to ReST markup

- Fix identation for the document title;
- use monotonic fonts for commands, paths, etc;
- use quote blocks where needed;
- adjust spaces to properly format paragraphs;
- add it to the user book.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>