Enhance Windowing compatibility with Librosa and SciPy

[palonso]

One of the goals of Essentia is to maximize parametrizability to allow compatibility with relevant implementations from other frameworks. The following feature requests for Windowing allow replicating some framing/windowing options from SciPy and Librosa:

• [x] Support SciPy-like hamming windows. While SciPy uses 2 decimals for the window parameters a0 and a1, Essentia uses 5. I propose the implementation of a general solution via a WindowParametersDecimals parameter that could rather bypass -1 or round to the n decimal the parameters used to build the windows for maximum flexibility.
• [x] Support asymmetric windows, as in SciPy.
• [x] Implement a splitPadding flag so that Windowing applies zero padding symmetrically and not only at the end of the frame when zeroPhase=False: splitPadding=False → /\__, splitPadding=True → _/\_. This option is bypassed when zeroPhase=True → \__/ (default). zeroPhase=False and splitPadding=True matches Librosa's behaviour.