Update osmGenus.txt

[davidpnewton]

Alphabetise, modernise taxonomy and increase number of entries

[Helium314]

Is the modernised data still coming from OSM?

[davidpnewton]

When I refer to "modernised" I mean bringing it in line with correct modern taxonomic standards. For example the inclusion of Aria and Scandosorbus is precisely that as they have been taken out of the complicated gestalt that Sorbus was and to some extent still is. Aria edulis and Scandosorbus intermedia are extremely common trees. Another example is × Hesperotropsis. That's a hybrid genus which contains × Hesperotropsis leylandii: it of the giant hedges causing neighbourly disputes the world over. Formerly that was in × Cupressocyparis, and it's an extremely common plant.

I've also made sure that all of the species mentioned in the species text file have their corresponding genus in this file. There was no obvious rhyme or reason for the genus being in there or not being in there in that respect.