[DOC] Documentation cleanups

[DOC] Documentation cleanups

Hi Willy,

This patch make some cleanups on the documentation :
- strictly respect the 80 columns constraint
- use space indentation everywhere
- add some missing "(deprecated)"
- fix the "monitor fail" keyword syntax
- fix a keyword in a "See Also" line (interval instead of inter)
- the "no" prefix of "option http-use-proxy-header" is displayed as the others

I've also noticed that 3 keywords are missing from the keywords reference (I don't know what to do for that) :
- dispatch
- reqsetbe
- reqisetbe

--
Cyril Bonté