added support for Spring XD Module packaging

Added XD_MODULE layout , a `moduleConfigRoot` parameter and IncludeFilter.  

e.g., typically, a module only needs a couple of dependent jars since it inherits the XD class path.
````
<build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
        <version>1.2.0.BUILD-SNAPSHOT</version>
        <configuration>
          <layout>XD_MODULE</layout>
          <!-- <finalName>${artifactId}</finalName>-->
          <includes>
          </includes>
        </configuration>
        <executions>
          <execution>
            <goals>
              <goal>repackage</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
````