[SPARK-16872][ML] Add Gaussian NB

[zhengruifeng]

What changes were proposed in this pull request?

Add Gaussian NB

How was this patch tested?

existing tests and added tests

[SparkQA]

Test build #79464 has finished for PR 18589 at commit ef89731.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #79489 has finished for PR 18589 at commit 75c82e1.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #79490 has finished for PR 18589 at commit 9044fb7.

• This patch fails MiMa tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #79491 has finished for PR 18589 at commit d71084a.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #79499 has finished for PR 18589 at commit b7b9206.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #79507 has finished for PR 18589 at commit ff1c6f9.

• This patch fails due to an unknown error code, -9.
• This patch merges cleanly.
• This patch adds no public classes.

[zhengruifeng]

Jenkins, retest this please

[SparkQA]

Test build #79509 has finished for PR 18589 at commit ff1c6f9.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[zhengruifeng]

Jenkins, retest this please

[SparkQA]

Test build #79516 has finished for PR 18589 at commit ff1c6f9.

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

[MLnick]

The previous PR had some discussion around whether this should be a new estimator or not. It's not clear why you've opened a new PR?

It's also not clear that decision was actually made. I think the consensus was more towards making GaussianNB a distinct estimator / model combination.

cc @sethah

[zhengruifeng]

@MLnick Sorry to reply late. It is a long time since I got the last comments in the previous PR #15324, so I thought that community may dislike that design.

I am still OK whether GNB be a distinct estimator or not. If someone can shepherd this the previous PR, I am OK to reopen it.

[SparkQA]

Test build #80672 has finished for PR 18589 at commit e71a069.

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

[SparkQA]

Test build #80677 has finished for PR 18589 at commit a9f8338.

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