Add Implementation of Remote and NetworkWorker

[yhdengh]

This PR is sequenced after #96

• Message

  • Add definitions of message headers and payloads for 4 message types: RUN, RESULT, REQUESTINFO, INFO
  • Add MessageParser for parsing incoming messages in a streaming way

• Remote

  • Each Remote object represents a remote Fix node
  • Each Remote owns a std::queue of tx_messages and install rules for moving tx_messages->RingBuffer->socket and
    socket->RingBuffer->MessageParser

• NetworkWorker

  • The NetworkWorker runs all rules of itself and all Remotes on a single eventloop.
  • It owns a moodycamel::concurrentqueue which will be accessed by both the eventloop thread and other worker threads.

• TODOs

  • Add EventFD to make the eventloop not polling-based
  • Delete entries from reply_to
  • Add unit tests

[Akshay-Srivatsan]

The network-tester is a standalone tester, not integrated into the test suite, right? We should probably have a unit test for it (and all this stuff) eventually.

[yhdengh]

The network-tester is a standalone tester, not integrated into the test suite, right? We should probably have a unit test for it (and all this stuff) eventually.

It is a standalone tester for now. Adding a "real" unit tester for the networking part is on my TODO list.