[#2042] Changed convo infrastructure to use Web Sockets.

[tonyanziano]

related to #1405 , #2042

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Highlights

• Activities from the bot are now sent to Web Chat over a Web Socket connection (no more endless polling / Network tab spam!!! 🎉🎉🎉)
• Pulled heavy-duty conversation initialization logic out of emulator.tsx component
  • this logic has been moved to botSagas.ts and chatSagas.ts so now they can be called more declaratively instead of relying on changes to props satisfying the right criteria
• Consolidated conversation creation logic so that opening a bot via .bot file, URL, or opening a transcript all flow through (more-or-less) the same code path
• Consolidated code path for opening a transcript via a .chat file versus a .transcript file
  • they essentially call the same code, except when handling a .chat file, we first use chatdown to convert the file to a transcript before extracting the activities
• Removed global user state
  • users are now scoped to the conversation level
  • no more having to call the SetCurrentUser command and manually maintaining the state
  • removed the users property from persisted server.json file (no more endless list of randomly generated user IDs from previous sessions)

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Passing E2E tests:

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Diagram of High-level Changes

[coveralls]

Coverage decreased (-0.4%) to 68.472% when pulling b29388f on toanzian/ws-final into cea9a86 on master.

[tonyanziano]

I think the coverage number has gone down as a result of removing a lot of tested code, but I will try to write some more to lessen the drop.

[tonyanziano]

Opened another PR with a bunch of new tests to compensate for drop in code coverage:

#2048

[srinaath]

Just a few comments or nice to have's.. Looks awesome 👍