Added Console Logging to HaaS

This patch adds console logging to HaaS by running ipmitool subprocesses that
log to files.  There is now an API call 'show_console' that displays the
contents of the console log to the user.  Log files are securely deleted when
nodes have a change in ownership.
So, we had some of this conversation in person, but we should really be pedantic about documenting it -- that's getting passed to the shell, so this is an arbitrary code excecution vulnerability if you can control that field. Only an administrator can do that though, so we're letting it go, at least for now. Let's write all that down.