Merge branch 'feature/high-performance-agent' of https://github.com/wu-sheng/sky-walking into feature/high-performance-agent

* 'feature/high-performance-agent' of https://github.com/wu-sheng/sky-walking:
  add logic of shade grpc

# Conflicts:
#	apm-sniffer/apm-agent/pom.xml

add logic of shade grpc

This reverts commit c52686f8.

Fix start collector image failed

fixed docker compose image path error

Improving agent

fixed #220

1. Change dag graph layout from hierarchical to relationship
2. Change node style from square to round

Finish almost all codes about ignore, sample and analytic trace mechanism. Left analytic trace only for collector.

Create CODE_OF_CONDUCT.md