DL-183: Configure DL to generate source jar
DL-183: Configure DL to generate source jar

also move the plugin version definition to the properties

Author: Sijie Guo <sijie@apache.org>

Reviewers: Jia Zhai <zhaijia@apache.org>

Closes #113 from sijie/sijie/generate_source and squashes the following commits:

6fa1ce5 [Sijie Guo] Merge branch 'master' into sijie/generate_source
d355d6a [Sijie Guo] Generate source jar during jar phase

sijie/incubator-distributedlog,sijie/incubator-distributedlog,sijie/incubator-distributedlog,sijie/incubator-distributedlog,sijie/incubator-distributedlog