Better numpy / general arithmetic

[jmg049]

There are a few gaps in using Spectrograms as a transparent ndarray.

Mostly this resolves around arithmetic and similar operations. Then also included the more "generic" versions, e.g. spectrogram * scalar (and scalar * spectrogram) or spectrogram * ndarrary (that is valid)

Basically the goal is no friction when using the Spectrograms alongside scalars and vectors / matrices / ndarray arrays / insert your favorite way of describing valid linear algebra, on these 2d arrays