Windows joins the version train

Windows only. The Windows app moves onto the Mac app's version numbers and gets faster chat and thread updates. This build aborted at startup on Windows; 0.1.9 fixes it.

Changed

Windows: version numbers match the Mac app from here on. Windows went from 0.1.4 to 0.1.8; nothing was skipped.
Windows: chat, thread, and notification updates arrive on a one-second long-poll, and chat lists load from SQLite summaries.