message/call views: ui overhaul

This patch:
- implements QWebEngineView as the view for interactions
- reorganizes the main widget's layout in order to share views
  between in-call and out-of-call messaging views
- fixes behavioral bugs and crashes
- cannot be built with the mingw compiler due to lack of support for
  QWebEngine, and must be built natively with msvc and includes some
  build script modifications
- should be thought of as a new client

Change-Id: I59d8c68dc8384e85fb006f30d8313482c00d6c85