merge in loggregator cf-release branch

* updates to new loggregator properties format
* add loggregator message signing support
* add loggregator logging to syslog aggregator
* bump loggregator version to 413 url https://github.com/cloudfoundry/loggregator/commit/b2dcf3c6fe38b4ce634ab78534ee501df79b8b46
fix api_z2 loggregator_endpoint property