- UI (previously MainUI) is back to being the only component loaded
as Window's child
- UI has the background image previously only for the SignInPage
- If there are no accounts, the UI Loader's initialItem is the
SignInPage
- The SidePane becomes visible when there's >=1 account connected
- Started work on the matrix-nio backend, which will be used instead
of matrix-python-sdk for greater control and cleaner design
- Have an Application (QGuiApplication) class to habdle argument parsing
and setting some Qt properties like application name
