[SPARK-1986][GraphX]move lib.Analytics to org.apache.spark.examples

to support ~/spark/bin/run-example GraphXAnalytics triangles
/soc-LiveJournal1.txt --numEPart=256

Author: Larry Xiao <xiaodi@sjtu.edu.cn>

Closes #1766 from larryxiao/1986 and squashes the following commits:

bb77cd9 [Larry Xiao] [SPARK-1986][GraphX]move lib.Analytics to org.apache.spark.examples