Add human mouse mix reference v3.1.0

Gervaise Henry
2019-07-31T14:35:46-05:00

Changes needed:
* [x] astrocyte_pkg.yml
* code has to be: GRCh38-and-mm10-3.1.0
* text should be 'Human GRCh38 + Mouse GRCm38 (mm10) release 93'
* put it directly above the two other human mouse mixes
* *NOTE: please fix mm19 to mm10*
* [x] biohpc.config
* In params:genomes: add the code from astrocyte_pkg.yml translation to physical location than Paniz will hopefully be making for us (see slack message)
* [x] README.md & index.md