[SPARK-13629][ML] Add binary toggle Param to CountVectorizer

## What changes were proposed in this pull request?

It would be handy to add a binary toggle Param to CountVectorizer, as in the scikit-learn one: http://scikit-learn.org/stable/modules/generated/sklearn.feature_extraction.text.CountVectorizer.html
If set, then all non-zero counts will be set to 1.

## How was this patch tested?

unit tests

Author: Yuhao Yang <hhbyyh@gmail.com>

Closes #11536 from hhbyyh/cvToggle.