Support providing yaml config in cli args

Our helmfile integration writes out yaml files, but we've been pretending those are properties files. This leads to issues where the yaml export breaks a string into multiple lines, but the parser treats it as two separate map entries. It additionally has issues where the yaml exporter decides to quote a string, but the properties parser has no concept of quoted strings.

Make things sane by directly supporting yaml files. This removes the mismatch between how config is written and how it is read.

Change-Id: If273afc02f56e31efd279b5983cc5c7a54ee3adf