This is a placeholder for what will be a series of patches to the FileList to generalize and enhance it.

This is part of generalizing pieces of IDLE to be more flexible, including things like editors not necessarily being in toplevel windows, dialogs not being modal, etc.

The goal is to turn the FileList into an application "hub" that knows about the various pieces of the application, and can be used for communication between them. Some aspects of this will include:

1. Ensuring other modules don't use internal implementation (e.g. dict/inversedict) so can change it later.

2. Merging PyShellFileList into here (will keep things simpler).

3. Having FileList launch/keep track of certain dialogs (e.g. config) or other non-editor components.

4. Eventually take on some other responsibilities from editors, part of a general component/container refactoring.