fixed the second item in #254: Use GRPC-java instead of HTTP rest which receive the trace segment from agent.

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

1. add global trace id column into segment cost index.
2. just query from segment cost index when query top segment record with condition, e.g. operation name, global trace id, cost

2. Change the http servlet worker from local asynchronous call to local synchronous call.

1. Remove the “apm-trace” module, isolate the trace structure between agent and collector for considering performance.
2. Change the head name.
3. Provide potienal mechanism for ignore trace with certain suffix.