Migration to AndroidX
- Update to API level 29
- Update Java sourcecode and xml import statements
- Upgrade Butterknife Version 10 AndroidX support
- Set Java 8 compile options due Butterknife needs it
- added method to HostConnection that returns a Future object instead of
taking a callback.
- added logic for handling null Handlers in HostConnection methods
- added method to HostManager to run a function that takes a HostConnection
in a background thread where the Future API results above can be
synchronously composed.
- replaced chain of callbacks in RemoteActivity with a sequence of
future gets in OpenSharedUrl.