Complete UI overhaul that gives DoNext a nice, modern look.
Complete code rewrite to Kotlin and Android Jetpack, with a better architecture.

Task lists are now displayed in a navigation menu
Tasks are now ordered by priority and not cycles
All tasks can be Done or Removed instead of only the first one
A Recycle Bin was added
The whole Next and cycles mechanism was removed
The History page was removed and its features split between the regular task lists and the Recycle Bin
The Today view is not a separate concept now, it's based on the tasks due date
No more Settings page as it's not needed anymore (but it may come back later if required)