Fix Packer, Upgrade Py3, modularise tests

[Chaffelson]

Rebased from current master and tested with direct deploy, packer, and pytest Significant restructuring of setup.sh to reduce deployment time to under 30mins Replace using system python2 with installed python3 to avoid breaking on reboot during Packer build Updated labs and images to py3 Fixed Packer to work with new builds Rename default Packer ami_name to 'cdfworkshop' to make it easier to find Added Packer test request to Contributing doc Reworked pytest Tests fpr py3 Set default execution for most python code to python3 Impala-shell lacks py3 compatibility, switched to native impyla for cleaner interfacing Added control SKIP_CDSW to skip cdsw tests if cdsw not built during deployment Added instructions to Contributing doc for pytest tests Added new TF_VAR_parallelism to .env.template to limit parallel deployment width Updated DockerFile to include Packer and Terraform by default, otherwise behaves the same

Other: Added null provider minimum version to Terraform to remove warning message Updated template to HTTPS endpoints for Cloudera.com and Maven.

[Chaffelson]

Fixes #13 Fixes #14

[Chaffelson]

About as tidy as I can get it with my broken fork. Once this is merged I'll reset the fork and reimplement the lab selection pieces.

[asdaraujo]

merged