Add inversion rules for SEMAPV cross-species predicates.

[gouttegd]

This PR updates the documentation to propose new inversion (“flipping”) rules for the cross-species predicates defined in the “semantic mapping vocabulary” (SEMAPV).

Specifically, it proposes that semapv:crossSpeciesExactMatch can be directly inverted, and that semapv:crossSpeciesNarrowMatch and semapv:crossSpeciesBroadMatch are mutually inverse. This follows the logic of the skos:{exact,narrow,broad}Match predicates upon which those cross-species variants are based.

semapv:crossSpeciesCloseMatch is not listed on purpose; the predicate is to be implicitly considered as “non-invertible”.

• docs/ have been added/updated
• make test has been run locally (not applicable, documentation change only)
• tests have been added/updated (likewise)
• CHANGELOG.md has been updated (deemed not necessary)

[matentzn]

Looks great! Thanks!