Remove docker document and docker plugin

The instance heart beat implementation of http JSON protocol.

Fixed/855

Create CONTRIBUTING.md

1. Use peer id in entry span to find the instance id and application id.
2. Make the instance id and application id to be the front instance id and front application id of the reference metric.
3. Do not create the application mapping metric.

Update NOTICE.txt

[Agent] fix create entry span failure

Add UI repo dependencies

Add the third Party Components description into notice file.

Remove Apache projects from NOTICE

Fixed/855

Fixed the getApplicationTopology bug, remove the application node which not contains the source or target of calls.

Fixed the number of application bug.

Update submodule/skywaling-ui

Submodule/update-ui

Fixed/855