Non-uniformed sampled signal not supported by SR

[RobertSamoilescu]

The current implementation of the SR outlier detector does not support non-uniformed sampled signals. This is due to FFT. A potential solution might be to investigate NFFT described in here and implemented in this repo. An alternative implementation can be found here.

[arnaudvl]

It could be possible to use keops to speed and scale this up as well.