Fix and rename Signal.find_peaks_1D

* Rename utils.one_dim_find_peaks to find_peaks_1D_ohaver
* utils.find_peaks_1D_ohaver returns a struct array instead of an array.
* Rename Signal.peakfind_1D to Signal.find_peaks_1D_ohaver.
* Make Signal.find_peaks_1D_ohaver work for ndimensional signals
* Add two tests for Signal.find_peaks_1D_ohaver