Auto-generate a secret key for django and store in the config file.

Auto-generate a secret key for django and store in the config file.
This way I can keep checking settings.py in.

Also since I implemented this be re-writing the settings file
I thought I'd clean out some of how we were storing some of our
previous default values. (Removed the hard coded - [defaults] section)
so they dont end up cluttering the users config file.

Since I removed the default for the linking hard disk tool
I changed the script to complain more helpfully if it can't find
the setting.