Updated battery repair documentation

[Daniel Drake]

Hi,

I've just published a rewrite of the battery troubleshooting/repair
documentation
at http://wiki.laptop.org/go/XO_Troubleshooting_Battery

This is based on recent experiences of battery repair with the help of
Richard Smith, adding new techniques and solutions.

Also, I restructured the content so that the page is more approachable
when you have a broken battery in your hands, and so that the content
is more succinct. Follow the "Start here" instructions step by step
and it'll take you to the appropriate section regarding the failure
condition that you're dealing with.

Another change is that all the content related to diagnosing
power/battery problems that are actually related to problems outside
of the battery has been moved here:
http://wiki.laptop.org/go/XO_Troubleshooting_Power
to further improve readability.
(maybe this new Power page needs a bit of work and more content - help
appreciated)

Thanks!
Daniel