[SPARK-19282][ML][SparkR] RandomForest Wrapper and GBT Wrapper return param "maxDepth" to R models

[keypointt]

What changes were proposed in this pull request?

RandomForest R Wrapper and GBT R Wrapper return param maxDepth to R models.

Below 4 R wrappers are changed:

• RandomForestClassificationWrapper
• RandomForestRegressionWrapper
• GBTClassificationWrapper
• GBTRegressionWrapper

How was this patch tested?

Test manually on my local machine.

[SparkQA]

Test build #74197 has finished for PR 17207 at commit 82612dd.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[felixcheung]

Can you clarify? this is on the model summary, not a param?

[keypointt]

sorry being vague, I updated the PR description just now

yes, it's for R model summary, R wrapper returning maxDepth to R model
as mentioned in the comment at https://issues.apache.org/jira/browse/SPARK-19282, I don't know how to find the RandomForestRegressionModel in the R docs. R does take the parameter, but it is unclear if it exposes it on the model.

[SparkQA]

Test build #74218 has finished for PR 17207 at commit d16b65c.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[felixcheung]

ok, great, could you update PR title and JIRA title then.

[felixcheung]

could you update the documentation on model summary in https://github.com/keypointt/spark/blob/d16b65cc077f3ba2a770d709cc8a7a9ebfda9aad/R/pkg/R/mllib_tree.R#L202

and

https://github.com/keypointt/spark/blob/d16b65cc077f3ba2a770d709cc8a7a9ebfda9aad/R/pkg/R/mllib_tree.R#L409

[SparkQA]

Test build #74250 has finished for PR 17207 at commit 477c4bc.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[keypointt]

Jenkins, retest this please

[SparkQA]

Test build #74271 has finished for PR 17207 at commit 477c4bc.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[keypointt]

ping @felixcheung

[felixcheung]

merged to master.