[bs-59] Add zip packaging for cli module

* Also added "spring" shell script (in zip), so you can
unzip it and run out of the box
* To run in developer mode use SPRING_HOME, e.g.

        $ cd spring-bootstrap-cli
        $ SPRING_HOME=target src/main/scripts/spring run samples/web.groovy
* Also added "clean" command to remove spring bootstrap grapes
(useful to force a refresh of snapshot jars)

[#48644271]

spring-bootstrap-cli/src/test/java/org/springframework/bootstrap/cli/SpringBootstrapCliTests.java

@@ -159,7 +159,7 @@ public class SpringBootstrapCliTests {
 		assertThat(new NoSuchOptionException("name").getMessage(),
 				equalTo("Unknown option: --name"));
 		assertThat(new NoSuchCommandException("name").getMessage(),
-				equalTo("spr: 'name' is not a valid command. See 'spr --help'."));
+				equalTo("spring: 'name' is not a valid command. See 'spring --help'."));
 	}
 
 	@Test