new TFR code

starts to implement what is described in : https://github.com/mne-tools/mne-python/issues/1333

for now only sensor space analysis is investigated.

it also adds a new dataset (somato) well adapted to TF analysis.
I wasn't suggesting that there should only be one parameter, but rather that it's strange to have them be in different units. We probably can't do anything about the issues you mention, since that's a Matplotlib issue. It's not really an issue in my mind so much as a different way of thinking about plots -- e.g., a 1 pt line should be 1 pt in width whether it's in a 2 in or 10 in figure. For a journal that requires lines of a specific point size it would be maddening to have lines scale with the image size. So there are advantages and disadvantages to having different parameters scale or not.