[SPARK-17197][ML][PYSPARK] PySpark LiR/LoR supports tree aggregation level configurable.

## What changes were proposed in this pull request?
[SPARK-17090](https://issues.apache.org/jira/browse/SPARK-17090) makes tree aggregation level in LiR/LoR configurable, this PR makes PySpark support this function.

## How was this patch tested?
Since ```aggregationDepth``` is an expert param, I'm not prefer to test it in doctest which is also used for example. Here is the offline test result:
![image](https://cloud.githubusercontent.com/assets/1962026/17879457/f83d7760-68a6-11e6-9936-d0a884d5d6ec.png)

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #14766 from yanboliang/spark-17197.