allow hybrid information

[mfrasca]

a hybrid should be described as a descendant of two taxa, not just flagged as such.

just to fix ideas, an example: you might want to indicate an accession to a taxon which is a hybrid between a masdevalia rosea and a dracula diavola.

hybrids do not need be sterile, so a hybrid could also generate a new hybrid if mixed with an other taxon.

not all taxa can be hybridized with each other, generally the parent taxa of a hybrid will belong to the same familia, subfamilia, tribus, or subtribus. maybe a warning could be issued if the two parents mismatch at too high a rank.

marking as 'prio:high' because this is really urgent if you want to represent a collection like the one at Quito, particularly dedicated to Orchidaceae.

[mfrasca]

This issue was moved to Bauble#179