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.
Hmm, I'm not a fan of this being a database field.  I was imagining it being a function 'self.get_console_log_file()' that returned this value.  @zenhack?