Merge pull request #1 from sparkprime/master

Add Jsonnet configuration language support.
Assumes _libjsonnet.so is in $PYTHONPATH.
Ignore backup files "*~".
Make Jsonnet optional; only require it if we're parsing a Jsonnet file.

Previously, loading this module would fail without the presence of _jsonnet.so
in PYTHONPATH leading the user unable to do anything without Jsonnet, even when
not using Jsonnet. With this change, lacking Jsonnet still allows user to parse
and evaluate Python and YAML files.
Added auto-generation of the VM images offline cache.
Use auto-generated VM images cache data instead of hand-written data.
Show overall status after running all tests; exit with proper code.
Exit with non-zero status code on error to propagate failures.
This patch does a few things

* avoids importing _jsonnet unless dynamically necessary.
* expects the list of resources returned from Jsonnet to be in a field called resources, instead of at the top level
* provides the GCP project name in the jsonnet "environment" (a feature I just added to Jsonnet to allow explicit passing of parameters to Jsonnet scripts).
Add Ambari example written in Jsonnet, with small variant
Merge remote-tracking branch 'upstream/master'

Conflicts:
	config_jsonnet.py
Merge branch 'master' into ambari_jsonnet