calendar.view.MainContainer: add a view model

Normally I don't use VMs for component creation.

The calendar is more like an app though, so it does make sense here:

We need to pass less configs to sub views and this enables you to use sub-views on their own (adding the VM).

Another benefit is that you can override "global" VM props with adding a VM for a child view. E.g. in case you want to use a different time format only inside the week view or only allow editing events there.