Generalize `dipole.ip_and_q`

[prisae]

The new (v2.5.0) function empymod.dipole.ip_and_q should work fine, but it is not well tested.

One thing it does is use the direct field of ab=66, if ab=[46,64], as those fields are zero, IF src_z==rec_z. If not, this does not apply.

Research the literature to generalize this function to correctly compute any src-rec combination!

• [x] Create functionality (#236, v2.5.0)
• [x] Fix bug, add warning (#238, #239, v2.5.1)
• [ ] Add tests (compare to SimPEG, FDEM1D), more extensive docs, and remove warning again
• [ ] Currently, the corresponding co-planar source-configuration is taken for the primary field. Make a choice of:
  • [x] Corresponding co-planar source-configuration (current implementation).
  • [ ] Actual configuration (which will be zero in certain configs and hence fail).
  • [ ] Total field: e.g., for any ab-config in [44, 54, 64]: sqrt({44}^2 + {54}^2 + {64}^2).
• [ ] Generalize to be also applicable for arbitrarily rotated dipoles (empymod.bipole)

[prisae]

#238 adds a warning, but does not resolve the issue as such.

[prisae]

#239 fixed the bugs, and released a new version 2.5.1.

[prisae]

Potentially related to this discussion: https://github.com/simpeg/simpeg/issues/1630