Rename bode and Bode plot

[pmli]

Based on return values of

• Matlab's bode,
• Matlab's freqresp,
• scipy.signal.bode,
• scipy.signal.freqresp,

and

• Matlab's frequency response definition

a better name for pymor.models.iosys.InputOutputModel.bode would be freqresp (python-control's freqresp is a bit different and behaves more like bode in Matlab and SciPy). Since underscores are common in pymor.models.iosys method names, I find freq_resp would be even better.

Additionally, this PR replaces "Bode plot" with "magnitude plot". I'm not sure if "magnitude plot" is a name for something or if there is a standard name for the plot of ||H(i omega)|| vs omega, but it seems that "Bode plot" and "Bode magnitude plot" refer to a grid of subplots with a column for each input and row for each output.

I would still prefer to have pymor.iosys.models.InputOutputModel.mag_plot, since it's commonly used to visualize the MOR error.

@sdrave Thoughts?

[sdrave]

@pmli, I think you should decide on this. Only two general remarks:

• Only rename the methods if you really think it improves user experience.
• I prefer Pythonic names over mimicking the interfaces of some other software. So I would prefer freq_resp over freqresp.

[pmli]

• Only rename the methods if you really think it improves user experience.

I already got comments that "bode" is misleading. This should help.

• I prefer Pythonic names over mimicking the interfaces of some other software. So I would prefer freq_resp over freqresp.

Alright, good.

There is still the issue with tests. @renefritze It seems there are some issues with debian and OSX.