Adds reset class decorator, removes nonzero kwarg

Since three of the process classes used the same (by now extremely
generalized) _reset method, I decided to turn it into a class decorator,
and moved it to the resources module, since it is most closely
associated with the MonitoredEnvironment class.  Also removed the
nonzero keyword argument from MonitoredEnvironment.register & related
methods, since it doesn't actually offer any utility, and was originally
added for debugging purposes.