* Reader API for C++ clienReader API for C++ clientt

* Fixed compile error with listener function

* Fixed compile errors and PR comments

* Fixed conversion between MessageId and BatchMessageId

* Removed usage of std::tie

* Revert change in BatchMessageId since it breaks the tracker

* Increase available permits only once

* Added reader endpoint description to WebSocket.md

* Fixed sample code in WebSocket.md

* Use on('message',listener) in node.js sample code

* Update `protobuf/README.md`

*Problem*:

the cpp protobuf files are automatically generated by Cmake.
we don't need extra instructions for generating cpp files.

*Solution*:

Remove the content about cpp from `protobuf/README.md`

* Update comment - "C++ code is automatically generated by cmake"

* Address comment

- add `event_time` field in message metadata proto
- expose `setEventTime` in MessageBuilder
- expose `getEventTime` in Message
- add event_time test cases for message & message builder

* Handle NPE at load-manager when leader couldn't find available broker

* avoid throwing exception

* return empty lookup-result if broker not found

* Validate dynamic-configuration value while updating or init

* Add msgAck and redelivery debug-logs And add topic-name in debug-logs

* Remove Managed Ledger metadata text format

* MockZookeeper should store values as byte[] and not convert to String

* Support setting private key content in athenz client plugin

* added privateKey field to authParams in athenz client plugin

* added new entrypoint for reader to websocket proxy

* supported non-persistent topic with websocket proxy

* added warn log in ReaderHandler

* call ReadeHandler.receiveMessage() on every readNext()

* receive ack from client in ReaderHandler

* hide apache feather on smaller screens

* apply hidden-md-down class to anchor rather than to image

* add get bundle api for a given topic-name

* add cli command to site

* Introduce message-dispatch rate limiting

read messages based on available-message-rate-permits

add admin command

add message-rate + byte-rate options for dispatch-rate limiting

policies on global-zk + combined msg/byte rate + reset rateLimiter-timeUnit

* address comment