kiji-mapreduce: KIJIMR-294. Add group ID to maven-archetype-plugin.

issue: https://jira.kiji.org/browse/KIJIMR-294
review: https://review.kiji.org/r/2065
commit: https://github.com/kijiproject/kiji-mapreduce/commit/011a9287e8228d901e7fd3f487148db304e8bff3