Allow user to specify classLoader as loader property

PropertiesLauncher now supports creating its own class loader
from looader.classLoader property. It will succeed if the
implementation specified has a default constructor or one
that takes a parent class loader, or one that takes a URL[]
and a parent class loader (like URLClassLoader).

spring-boot-cli/pom.xml

@@ -233,11 +233,14 @@
 							<archive>
 								<manifest>
 									<addDefaultImplementationEntries>true</addDefaultImplementationEntries>
-									<mainClass>org.springframework.boot.loader.JarLauncher</mainClass>
+									<mainClass>org.springframework.boot.loader.PropertiesLauncher</mainClass>
 								</manifest>
 								<manifestEntries>
 									<Start-Class>${start-class}</Start-Class>
 								</manifestEntries>
+								<manifestEntries>
+									<Class-Loader>groovy.lang.GroovyClassLoader</Class-Loader>
+								</manifestEntries>
 							</archive>
 						</configuration>
 					</execution>