switch packaging to pom (#102)

instead of manually disabling plugins from jar packaging
diff --git a/johnzon-distribution/pom.xml b/johnzon-distribution/pom.xml
index e77d1ee..f91dc17 100644
--- a/johnzon-distribution/pom.xml
+++ b/johnzon-distribution/pom.xml
@@ -26,6 +26,7 @@
   <modelVersion>4.0.0</modelVersion>
 
   <artifactId>apache-johnzon</artifactId>
+  <packaging>pom</packaging>
   <name>Johnzon :: Distribution</name>
 
   <dependencies>
@@ -197,27 +198,6 @@
       </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-source-plugin</artifactId>
-        <configuration>
-          <skipSource>true</skipSource>
-        </configuration>
-      </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-jar-plugin</artifactId>
-        <configuration>
-          <skipIfEmpty>false</skipIfEmpty>
-        </configuration>
-      </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-javadoc-plugin</artifactId>
-        <configuration>
-          <skip>true</skip>
-        </configuration>
-      </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-site-plugin</artifactId>
         <configuration>
           <skip>true</skip>