[SPARK-10981] [SPARKR] SparkR Join improvements

I was having issues with collect() and orderBy() in Spark 1.5.0 so I used the DataFrame.R file and test_sparkSQL.R file from the Spark 1.5.1 download. I only modified the join() function in DataFrame.R to include "full", "fullouter", "left", "right", and "leftsemi" and added corresponding test cases in the test for join() and merge() in test_sparkSQL.R file.
Pull request because I filed this JIRA bug report:
https://issues.apache.org/jira/browse/SPARK-10981

Author: Monica Liu <liu.monica.f@gmail.com>

Closes #9029 from mfliu/master.