Fixes, updates, streamlining

Hi Jeff,

Here are my changes to kirkwood.debian-wheezy.sh, as originally posted on the forum (plus a few new bits). Because the other Squeeze/Wheezy install scripts share a lot of the same code, I've also applied the same changes to them in subsequent commits. (I tested the two Squeeze install scripts, minus the flash parts and actual booting, to suss out the differences with Wheezy.) Plus, there's a couple minor touch-ups to index.htm.

Please review the changes, and let me know if they need any more work.