Rename ComposableView to App

src/main.rs

src/ui.rs

src/ui/app.rs

src/ui/panes.rs

src/ui/panes/default.rs

src/ui/panes/messages_viewer.rs

src/ui/panes/plot.rs

src/ui/persistency/layout_manager.rs

src/ui/persistency/layout_manager_window.rs

src/ui/widget_gallery.rs