Iblatlas

Modified
- `iblatlas.plots` uses matplotlib.colormaps.get_cmap instead of deprecated cm.get_cmap

Modified
- `iblatlas.plots` uses colors.get_cmap instead of deprecated colors.get_cmap

Modified
- `iblatlas.genomics.merfish.load` does not return an error when dask is installed but
dask.dataframe is not.

Added
- `iblatlas.genomics.merfish` module for working with the Allen gene expression
atlas in the `iblatlas.genomics.merfish` module

Added
- `iblatlas.genomics.agea` module for working with the Allen gene expression
atlas in the `iblatlas.genomics.agea` module
Modified
- slices of the atlas are now always returned with consistent sizes regardless of the volume layout on disk
- atlases now can have an extra dimension in the image volume, to allow for multiple layers

Modified
- Insertion._get_surface_intersection: can return None if and when mode is not set to raise and insertion is not intersecting with any surface
- BrainAtlas.mask(): method that computes a mask of the convex brain volume shape