Add `getStaticClass` method in SparkR's `RBackendHandler`
This is a fix for the problem referenced in [SPARK-5185](https://issues.apache.org/jira/browse/SPARK-5185).
cc shivaram
Author: cafreeman <cfreeman@alteryx.com>
Closes#7001 from cafreeman/branch-1.4 and squashes the following commits:
8f81194 [cafreeman] Add missing license
31aedcf [cafreeman] Refactor test to call an external R script
2c22073 [cafreeman] Merge branch 'branch-1.4' of github.com:apache/spark into branch-1.4
0bea809 [cafreeman] Fixed relative path issue and added smaller JAR
ee25e60 [cafreeman] Merge branch 'branch-1.4' of github.com:apache/spark into branch-1.4
9a5c362 [cafreeman] test for including JAR when launching sparkContext
9101223 [cafreeman] Merge branch 'branch-1.4' of github.com:apache/spark into branch-1.4
5a80844 [cafreeman] Fix style nits
7c6bd0c [cafreeman] [SPARK-8607] SparkR
(cherry picked from commit 2579948bf5)
Signed-off-by: Shivaram Venkataraman <shivaram@cs.berkeley.edu>