Raw read/write methods only support AI/AO

[bkeryan]

In the DAQmx LV and C APIs, the raw read/write functions support all channel types including DIO and counters. However, the nidaqmx-python raw read/write methods (task.in_stream.read and task.out_stream.write) query AI/AO-specific properties in order to determine the raw data format. Calling these methods on a DIO or counter task will error because these AI/AO-specific properties are not supported.