Expose the Tasks as a Calendar (with an option)

[BalooRJ1]

Per chat conversation with @tasn and @fastcat001, requesting support for Davx5 Tasks compatibility in Etesync so as to place both Tasks and Calendar into one synced Etesync calendar.

[tasn]

Thanks! It's very similar to #32, once we do one, we can easily do the other!

[betsythefc]

I'm unsure if what is described here is what I want, but I think having one journal/collection that I can put both calendar events and tasks into would be great. I wanted to created one journal for my education to put due dates, terms, drop dates in, and to add tasks for assignments. I know I can do two journals, but figured one was cleaner.