Make agent gRPC to be a collector module.
Make agent jetty to be a collector module.
Make agent stream to be a collector module.

Feature/stream jetty

Trace segment compute by http json stream test success.

Appand modules: apm-collector-baseline and apm-collector-baseline-computing for jd contributor team.

Provide new collector modelization core and graph streaming core

Merge branch 'feature/collector-modelization' of https://github.com/OpenSkywalking/skywalking into feature/collector-modelization

Merge branch 'feature/collector-modelization' of https://github.com/OpenSkywalking/skywalking into feature/collector-modelization

Add Span amount control mechanism, also memory limit mechanism

* Update architecture graph.
* Update REAMDME.

* feature/collector-modelization: (55 commits)
  Change the exception to runtime exception in module find and service find method.
  Register graph finish.
  Application register test success.
  Fix a code style issue.
  Move instruments into an independency module in collector, named `apm-collector-instrument`.
  Remove ServiceInstrumentation mechanism for further collector agent design.
  Adjust startup sequence.
  cluster, naming, grpc manager, jetty manager, storage modules test successful.
  Segment standardization
  Parse and listener
  trace workers
  Register workers
  no message
  Add cache service manager in worker construction.
  Fix compile issues.
  Support WayToNode for entry node.
  JVM worker
  Use cache service from cache module.
  Refactor cache module to provide cache services.
  Fix a pom confilct.
  ...

Merge branch 'feature/collector-modelization' of https://github.com/OpenSkywalking/skywalking into feature/collector-modelization