SPARK-1387. Update build plugins, avoid plugin version warning, centralize versions

Another handful of small build changes to organize and standardize a bit, and avoid warnings: 

- Update Maven plugin versions for good measure 
- Since plugins need maven 3.0.4 already, require it explicitly (<3.0.4 had some bugs anyway) 
- Use variables to define versions across dependencies where they should move in lock step 
- ... and make this consistent between Maven/SBT

OK, I also updated the JIRA URL while I was at it here.