* metrics: support dynamic configuration settings
* add test
* trace: update configuration when settings change
* config: allow logging options to be configured when settings change
* envoy: allow changing log settings
* fix unexpected doc change
* fix tests
* pick a port at random
* update based on review
- Update envoy bootstrap config to protobufs
- Reorganize tracing config to avoid cyclic import
- Push down zipkin config to Envoy
- Update tracing options to provide sample rate