Document qcontrol backport for wheezy

Automatic fan regulation is now possible, as are some other things.  Thanks
to Ian Campbell for his work on qcontrol!
DNS-323: Document workaround for missing /dev/disk/by-uuid link bug
Document problems with connecting to the serial on plug computers

Suggested by "marko".
Update DNS-323 known issues

Bug #622325 was fixed in kernel 3.2.53-1
Remove stray line
Fix formatting issue by putting &nbsp; outside of code block
Merge pull request #1 from tbm/master

latest from Martin