[SPARK-17157][SPARKR] Add multiclass logistic regression SparkR Wrapper

## What changes were proposed in this pull request?

As we discussed in #14818, I added a separate R wrapper spark.logit for logistic regression.

This single interface supports both binary and multinomial logistic regression. It also has "predict" and "summary" for binary logistic regression.

## How was this patch tested?

New unit tests are added.

Author: wm624@hotmail.com <wm624@hotmail.com>

Closes #15365 from wangmiao1981/glm.