Ooipy

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- several bug fixes and improvements in documentation
- fixed calibration for Axial Base broadband hydrophone

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- bug fixes in spectrogram computation and package installation

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- bug fixes in multiprocessing functions and hydrophone sensitivity correction

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* added HydrophoneData.wave_write()
* HydrophoneData.plot_timeseries()
* updated ooipy_demo.ipynb
* added deprecation warning to Spectrogram.visualize()
* added Spectrogram.plot() (calls tools.ooipypltlib.spectrogram_plot())
* added deprecation warning to PSD.visualize()
* psd.plot()
* node string format change for broadband and low frequency hydrophones (removed '/')
* sensitivity correction for all broadband hydrophones
* sensitivity correction for low frequency hydrophones
* added request/ctd_request.py module
* added ctd/basic.py module for extracting CTD data and computing parameter profiles over the water column

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* dependencies are installed properly when using pip

* minor changes on documentation
* minor bug fixes in spectrogram computation and visualization