Add ValueProvider for command names, use in "help"

Also, add some cases to samples

Fixes #42

Add tests

spring-shell2-samples/src/main/java/org/springframework/shell2/samples/legacy/LegacyCommands.java

@@ -21,11 +21,13 @@ import java.lang.reflect.Method;
 import org.springframework.shell.core.CommandMarker;
 import org.springframework.shell.core.annotation.CliCommand;
 import org.springframework.shell.core.annotation.CliOption;
+import org.springframework.stereotype.Component;
 import org.springframework.util.ReflectionUtils;
 
 /**
  * Created by ericbottard on 09/12/15.
  */
+@Component
 public class LegacyCommands implements CommandMarker {
 
 	public static final Method REGISTER_METHOD = ReflectionUtils.findMethod(LegacyCommands.class, "register", String.class, ArtifactType.class, String.class, boolean.class);

spring-shell2-samples/src/main/java/org/springframework/shell2/samples/standard/Commands.java

@@ -16,6 +16,9 @@
 
 package org.springframework.shell2.samples.standard;
 
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Target;
+
 import org.springframework.shell2.standard.ShellComponent;
 import org.springframework.shell2.standard.ShellMethod;
 
@@ -46,4 +49,9 @@ public class Commands {
 	public int add(int ahbahdisdonc, int b, int c) {
 		return ahbahdisdonc + b + c;
 	}
+
+	@ShellMethod(help = "Fails with an exception")
+	public void fail(ElementType elementType) {
+		throw new IllegalArgumentException("You said " + elementType);
+	}
 }