Update plots for matplotlib 2.0

[mgeier]

The new version (which will be released in January 2017) has a few changes which affect our plots.

For a list of changes see http://matplotlib.org/2.0.0rc2/users/whats_new.html and http://matplotlib.org/2.0.0rc2/users/dflt_style_changes.html.

I've noticed several differences:

• Image interpolation has changed, which makes our plots look more pixelated (but I guess more accurate, too?). We should increase the grid resolution of the examples or find some other way to make them look nicer.

• The grid lines seem to be drawn over the loudspeaker symbols, we should bring the loudspeakers up again.

• The grid lines seem to have changed from dotted to solid grey, we should check if we like that.

• For some reason the grid lines are not equally spaced on x and y axis anymore in the loudspeaker array examples

• The loudspeaker numbers may be cut off by the border of the plot. This was brittle anyway, maybe we find a better way to make sure they are shown correctly.

Feel free to add more points here.

[mgeier]

It's done: http://matplotlib.1069221.n5.nabble.com/REL-matplotlib-v2-0-0-td47749.html

http://matplotlib.org/users/whats_new.html#new-in-matplotlib-2-0