File behaviour

What's the expected behaviour of the file settings?

Goals, in order

1. Act exactly like PuTTY if there are no file settings, until the user asks for files.
2. Don't read or write the registry if there are file settings, unless the user asks for registry.
3. Have some logical behaviour for Default Settings.

Primitives

1. Do we have any registry settings?
2. Do we have any file settings?
3. Do we have Default Settings in the registry?
4. Do we have Default Settings in files?

..

when reg, and file is selected {
  mode -> file
  load defaults
}

and v.v.?