Flatten exception classes

The exception classes for the control environment are three deep: Error <- ErrorControl <- ErrorControl*. This grouping a bunch of error classes under ErrorControl has not proved to be very helpful. Furthermore, having Control as part of the name is probably unnecessarily verbose.

I propose flattening this hierarchy a bit by first removing the ErrorControl class. All the exception classes that inherit from ErrorControl will change to inherit directly from Error. Furthermore, "Control" will be removed from all the names. For example, ErrorControlBadValue will be changed to ErrorBadValue.