Create examples for the Bigtable Spark connector in Java, Scala, and Python

[rkaregar]

Description

Create sample projects for Cloud Bigtable Apache Spark Connector Private Preview phase.

[anguillanneuf]

@rkaregar pls fix license header in your files; this repo is meant for samples planned to be published on cloud.google.com, i don't see any START END region tags (1) for docs samples inclusion, could you work with the TW to have those created first? check out other samples in the repo for reference and go/code-snippets-101

pls also ping @billyjacobson for a review

[rkaregar]

@rkaregar pls fix license header in your files; this repo is meant for samples planned to be published on cloud.google.com, i don't see any START END region tags (1) for docs samples inclusion, could you work with the TW to have those created first? check out other samples in the repo for reference and go/code-snippets-101

pls also ping @billyjacobson for a review

Hi @anguillanneuf, thanks for the feedback. This PR is intended only for a private preview phase, we're not aiming to submit it for the official cloud docs and will delete it once the preview is over.