Make Catalog browsers focusable with shortcuts

- Category and scenario list views can now be focused with
  ctrl+a/ctrl+s.
- Bind all keys with ctrl modifier
- Add "shortcut" concept to views which currently hooks to
  hot keys.
- In a catalog app by using a "shortcut" then takes the key
  event as a hot key, as it consumes resulting behaviour
  is to focus.
- Move view initInternal away from constructor call to
  require user to call init() which is not in a
  View interface
- Relates #826

spring-shell-docs/src/test/java/org/springframework/shell/docs/TerminalUiSnippets.java

@@ -38,6 +38,7 @@ class TerminalUiSnippets {
 		void sample() {
 			TerminalUI ui = builder.build();
 			BoxView view = new BoxView();
+			ui.configure(view);
 			view.setDrawFunction((screen, rect) -> {
 				screen.writerBuilder()
 					.build()
@@ -59,6 +60,7 @@ class TerminalUiSnippets {
 		void sample() {
 			TerminalUI ui = new TerminalUI(terminal);
 			BoxView view = new BoxView();
+			ui.configure(view);
 			ui.setRoot(view, true);
 			EventLoop eventLoop = ui.getEventLoop();
 			eventLoop.keyEvents()