Previously a lot of things would start running concurrently at
startup as we were setting up the UI. This removes a considerable
amount of perceived delay.
Note: there are better ways to make sure forms are populated when they
are viewed, such as each widget's `showEvent()`
This allows to complete from relative paths, such use exe override
Fix constructor argument names to follow Qt's types.
Set the same filters as the dialog for the completer.
Use the completer's icon provider for the dialog.
Force Rare to use Qt's file dialog instead of the native one.
