Follow FluidUi.Settings API changes

API is changed.
Default settings

Assume some default settings.
Use FluiUi.Icon for AppChooser icons
Comment various file groups

This makes it more readable.
Simple dialog

A first raw implementation of a dialog.

Issue: #17
Rename AppChooserStyle to DialogStyle

We want the same style for all dialogs and so we reuse the former
AppChooser style.

Issue: #17
Make AppChooser a dialog

AppChooser window is now a dialog.

Issue: #17
Shutdown dialog

Dialog to reboot or power off.

Issue: #13