Major UI overhaul

- [x] remove Caliburn. I prefer explicit binding of properties and commands.
- [x] IoC, use a decent dependency injection container instead of MEF (fixes #2)
- [x] streamline UI, use bigger fonts (fixes #6 too)
  - make use of [MahApp.Metro](http://mahapps.com/MahApps.Metro/)s flyouts for certain dialogs
  - nicer UI for remaining dialogs
- [x] use `async`/`await` where appropriate
- [ ] add/remove assemblies in setup