Completion proposal support for complete jline parameter

- to allow completing single argument with multiple tab clicks,
  for example file paths.
- Backport #512
- Fixes #836

spring-shell-autoconfigure/src/main/java/org/springframework/shell/boot/CompleterAutoConfiguration.java

@@ -63,7 +63,7 @@ public class CompleterAutoConfiguration {
 					p.description(),
 					null,
 					null,
-					true)
+					p.complete())
 				)
 				.forEach(candidates::add);
 		}