This is useful for both cleanly exiting from simulation and for unit testing
at a framework level.
This change required removing move constructor/assignment from IterativeRobot.
Since https://github.com/wpilibsuite/allwpilib/issues/786 has been
closed as not a legitimate concern, there is now no reason to use
IterativeRobot over TimedRobot. It's a drop-in replacement that's
strictly an improvement in terms of execution jitter.
To migrate, one simply has to replace the IterativeRobot subclass in
their robot code with TimedRobot.
The old headers were moved into folders because doing so avoids polluting
the system include directories.
Folder names were also normalized to lowercase.
