is-sensor plot hints

[ddkohler]

For automated plotting, it is convenient for sensors to tell clients info about how the data should be viewed. This is especially true for 2D plotting (e.g. pcolor), where the colormap and its bounds/scale strongly influence how the data can be seen (examples of such plotting info is the sign attribute of WrightTools channels, or the norm objects of matplotlib colormaps). I am hoping we can implement plot hints for the is-sensor trait.

My proposed implementation is simply adding a message exposing whether or not channal data is signed, but I am not certain how basic or advanced hints should be. In theory, you could be more informative (for an example, see this discussion re: a WrightGroup proposals to rewrite the WrightTools.Channel plot hint attributes). Interested on thoughts from others...