Create 1-d Morlet and Gabor wavelets

Create functions for the 1-d versions of the Morlet and Gabor wavelets.

Optionally port definitions of https://github.com/scatnet/scatnet/blob/master/filters/morlet_filter_bank_1d.m
providing licensing information in a NOTICE.txt crediting the original works.

1. Define wavelets in physical units, i.e. bandwidth and center frequency in hertz (require input of sample frequency).
2. Provide a "factory" method to generate wavelets according to the dimensionless defaults used in https://github.com/kymatio, or https://github.com/scatnet. This provides a way for people familiar with these libraries to reuse existing definitions, can we may use these libraries for testing.
3. Provide a method for "cropping" the wavelet to reduce the cost of convolutions, cropping should be a function of something like bandwidth.
4. (optional) apply a taper to avoid issues in the spectrum of cropping the wavelet.