Support access to console log

Any time someone would file a bug against an image, we are going to want to get access to the console log to see what is going on.

The cloud images write their log to the serial console (/dev/ttyS0).
So please log this to a file so the user could get access to it.

Read/write access to the serial console would be nice too, though read-only access would be the biggest step forward in usefulness.