Add private, minor formatting.
Add RDD.coalesce.
Remove unneeded zipWithIndex.

Also rename r->rdd and remove unneeded extra type info.
Clean up RDDs, mainly to use getSplits.

Also made sure clearDependencies() was calling super, to ensure
the getSplits/getDependencies vars in the RDD base class get
cleaned up.
Remove RDD.coalesce default arguments.
Add back return types.
Fix JavaRDDLike.coalesce return type.
Move JavaRDDLike.coalesce into the right places.
Merge pull request #452 from stephenh/misc

Add RDD.coalesce, clean up some RDDs, other misc.