Remove spectral distances?

[lazappi]

Currently there is a control method and distance correlation metric that uses spectral distances. This is not a common metric and I'm not sure what it adds to the benchmark so I would be inclined to remove/disable it. I'm happy to hear arguments for why it would be useful to keep though.

[lazappi]

@scottgigante I think maybe you introduced this? Do you have thoughts on if it's important to keep?