Removed the Visitor prefix from most of the types in Checkpoint.
VisitorSolution -> Solution
Dropped Visitor prefix from all types in the Path module.
VisitorWorkload --> Workload
Removed Visitor prefix from all types (and fields) in the Worker module.
Cosmetic: Fixed missing fold markers in Main.
Made the callback names in Supervisor consistent with everything else.
Fixed unintended renaming of forkVisitorWorkerThread.