Move useful_addresses.html to the wiki

[khali]

I propose that we move doc/useful_addresses.html to lm-sensors.org/wiki. Reasons for that are:

• It will be much more visible there. I don't expect users to find this file under /usr/share/doc. Some distributions don't even package it.
• It is version-independent.
• It will be easier to maintain in the wiki, more people can change it there so there is a chance that the document becomes more useful over time.

If nothing else, this will be one less file to keep in sync between both lm-sensors branches.