Add complexity estimate feature calculators

[MaxBenChrist]

This paper defines a estimate of the complexity of a time series.

http://www.cs.ucr.edu/~eamonn/Complexity-Invariant%20Distance%20Measure.pdf

I would like to add that feature.

Edit: the respective journal paper discusses 8 different measure for the complexity of a time series, e.g.

• Fractal dimension
• Absolute difference
• Compression
• Pseudo-pairs
• edges
• zero-crossings
• spektrum
• fourier entropy
• permutations entropy

I implemented the complexity estimate measure used in CID. I will leave this issue open as a starting point for new features

[MaxBenChrist]

pr #332 contains the cid complexity estiator

[nils-braun]

I implemented the fourier entropy in #688.

[nils-braun]

and the permutation entropy in #691

[nils-braun]

absolute differences and zero crossings are already implemented.
That leaves us with:

• Fractal dimension
• Compression -> might be very slow
• Pseudo-pairs
• edges
• spektrum

I will keep this issue open but I do not plan to implement more of them in the near future