Minor Doc update - add SparkR to spark interpreter docs
Minor Doc update - add SparkR to spark interpreter docs

### What is this PR for?
Minor documentation update that mentions the SparkR interpreter.
Minor grammar updates.

### What type of PR is it?
Documentation

### Questions:
* Does the licenses files need update? No
* Is there breaking changes for older versions? No
* Does this needs documentation? No

Author: Jeff Steinmetz <jeffrey.steinmetz@gmail.com>

Closes #840 from jeffsteinmetz/minor-spark-doc-update and squashes the following commits:

a00d6a7 [Jeff Steinmetz] fix merge conflicts
5969a73 [Jeff Steinmetz] add SparkR to spark interpreter docs

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