Create removable drive manager and reader/writer tasks
requested to merge 2016-2017-2018-removable-drive-reader-writer into 1802-sync-via-removable-storage
This branch adds a RemovableDriveManager that allows the UI to start and observe tasks that read from/write to removable drives.
Closes #2016 (closed), #2017 (closed), #2018 (closed)