Add executions for maven-assembly-plugin.

Add the executions steps to produce a single archive with all the jars,
scripts and configuration files.

Author: Franck Cuny <fcuny@twitter.com>

Reviewers: Sijie Guo <sijie@apache.org>

Closes #42 from franckcuny/fcuny/maven-assembly
diff --git a/bookkeeper-server/pom.xml b/bookkeeper-server/pom.xml
index 7e63c3a..81e4532 100644
--- a/bookkeeper-server/pom.xml
+++ b/bookkeeper-server/pom.xml
@@ -252,6 +252,14 @@
             <descriptor>../src/assemble/bin.xml</descriptor>
           </descriptors>
         </configuration>
+        <executions>
+          <execution>
+            <phase>package</phase>
+            <goals>
+              <goal>single</goal>
+            </goals>
+          </execution>
+        </executions>
       </plugin>
       <plugin>
         <groupId>org.apache.rat</groupId>