wimsy should capture Windows installer logs from guest

[wfchandler]

When the Windows installer fails due to an invalid product key there is no on-screen indication of what went wrong, and presumably there are many other failure modes where this may occur as well. Manually connecting to the guest and opening a cmd prompt to view the logs is slow and requires some Windows knowledge.

It would be useful for wimsy to collect any installer logs from the guest machine and include them in its own logs.