Remove obsolete code: RoundedButton

[marc-medley]

Remove obsolete code RoundedButton.

Replacement of RoundedButton with UIButton elements (and adding some programmatic settings) fixed first launch settings. See Issue #65.

The remaining section to be migrated from RoundedButton with UIButton is the HistoryLayout storyboards and the associated ControlPanel.

This is a step towards reducing code complexity and reducing the InterfaceBuilder type settings. SwiftUI does not use the InterfaceBuilder.