Remove the error when ranks of synonym/etc. don't match

[mclapham]

The error "The rank of a taxon and the rank of its synonym, homonym, or replacement name must be the same" should not exist. Because of the principle of coordination, a subgenus - e.g. Lonsdaleia (Waagenella) - can be replaced by a genus - e.g. Waagenophyllum - without changing the rank of that subgenus. Same for tribe/subfamily/family etc.