Added extension host process that launches from main process

[tjcouch-sil]

• Added extension host process that launches from main process. Has some test command handlers
  • Watchers automatically restart it with nodemon
  • Extension host has its own webpack configuration and exports to its own js bundle
  • When launched through VS Code, breakpoints hit on both main and extension host
  • When launched outside of VS Code, extension host console logs and errors are logged with {eh} prefix and {/eh} postfix
• Added localStorage polyfill on the Node processes. Goes to %appdata%/paranext-core
• Added src/client folder for shared modules between the renderer and the extension host
• Added src/node folder for shared modules between main and extension host
• Added retrying websocket connection on clients
• Removed request registrations on client disconnect
• Split out WebSocket in ClientNetworkConnector.ts into WebSocketFactory.ts that loads browser WebSocket in renderer and ws's WebSocket in Node (extension host)
• Various fixes

Relates to #7 and #16

[irahopkinson]

Thanks for all your good work on this. I've done a first pass over this to keep it moving forward.

[irahopkinson]

I see you have auto-merge enabled. When I end up approving this PR it could merge before #43.

[irahopkinson]

👍 LGTM