We'll be needing it for packed.load, so it's not binarywave-specific.

Also moved byte_order to the util module and renamed a few functions
internal to the binarywave module so they start with an underscore.

The loadibw -> load (and saveibw -> save) change is because

  from igor.binarywave import load

gives you enough of an idea about what you're importing.  If you want
to keep it explicit in your client module, use

  from igor.binarywave import load as loadibw

which we do in the test.py module.

Samples are from TN003.zip, downloaded from
  ftp://www.wavemetrics.net/IgorPro/Technical_Notes/TN003.zip

I'm confident in the bytes -> strings conversion, but not entirely
sure how the strings get mapped into multidimensional arrays.

Otherwise an earier switch to a non-native byte ordering will confuse
the current load.

It's a utility for the MFP3D driver, not a driver in its own right.