Renaming across the MARQOV namespace

Now that the entry point for users is the scheduler we need to perform a renaming across the namespace:

• MARQOV::MARQOVScheduler -> MARQOV::Scheduler
• MARQOV::MARQOV -> MARQOV::MC (any other ideas?)
• MARQOV::MARQOVQueue -> MARQOV::TaskQueue (maybe I'll open up another namespace for scheduling related things)