Squeeze

• The main modelling routines bipole, dipole, loop, and
  analytical take a new keyword argument squeeze, which is set to
  True by default. If true, the output is squeezed (status quo); if false,
  the output is always a three-dimensional array (nfreqtime, nrec, nsrc).

• One can define new +np.infty as interface. Only use-case is to enforce a
  coordinate system in a two-layer case with an interface at z (see example
  coordinate system in the educational section of the gallery).

• Documentation:

  • Expanded note on FFTLog.
  • Expanded note on coordinate system.
  • Changed the description from optional to default: xyz in the main
    modelling routines.

• Maintenance:

  • Use scipy through conda in CI.
  • Fix do_3d_projection for matplotlib>3.5.0.