[Feature] Allen Common Coordinate Framework Version 2

[PolarBean]

Publication: https://doi.org/10.1038/nature05453
Template: https://download.alleninstitute.org/informatics-archive/current-release/mouse_ccf/ara_nissl/
Segmentation: https://download.alleninstitute.org/informatics-archive/current-release/mouse_ccf/annotation/mouse_2011/

I know it has been superseded by the CCFv3 however it's important for historical reasons and is in a distinct space. Also @Sebastien-PILUSO developed a transformation between this volume and the CCFv3 that I would like to integrate into CCF translator and so it would be nice to have in the atlasapi.