Provide a complete mapping of UCSC chromosome names to Ensembl

[jorainer]

@ivanek opened an issue over at ensembldb (https://github.com/jotsetung/ensembldb/issues/88). ensembldb in general uses the genomeStyles function from GenomeInfoDb to map chromosome names. As of now we can only map the standard chromosome names from UCSC to Ensembl. It would also be nice to be able to map names for patched chromosomes etc. Eventually Robert's solution mentioned over at the ensembldb issue might be a starting point?