Improve MGI mapping
Improve MGI mapping

This can now map using Ensembl and keeps better counts. This version can
map just over 50% of all given entries which is pretty good so far.

RNAcentral/rnacentral-webcode,RNAcentral/rnacentral-webcode,RNAcentral/rnacentral-webcode,RNAcentral/rnacentral-webcode