[3.1] kikuchipy extra, EBSD signal type, IO, detector geometry

[CSSFrancis]

• ebsd extra; EBSD signal type recognised and gated.
• IO through kikuchipy's readers: .h5/.h5oina, .ang, EDAX / Oxford / Bruker formats.
• EBSDDetector geometry panel (projection centre, tilt, binning, shape).

Detector geometry is load-bearing for [3.3] and [3.4] — get the panel right before the indexing work starts.

Part of #68.

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Plan: RELEASE_0_3_0_PLAN.md