[SPARK-6856] [R] Make RDD information more useful in SparkR

Author: Jeff Harrison <jeffrharrison@gmail.com>

Closes #5667 from His-name-is-Joof/joofspark and squashes the following commits:

f8814a6 [Jeff Harrison] newline added after RDD show() output
4d9d972 [Jeff Harrison] Merge branch 'master' into joofspark
9d2295e [Jeff Harrison] parallelize with 1:10
878b830 [Jeff Harrison] Merge branch 'master' into joofspark
c8c0b80 [Jeff Harrison] add test for RDD function show()
123be65 [Jeff Harrison] SPARK-6856