scprep v0.12.0

Changeset:

• added scprep.run.splatter, a Python port of the Bioconductor Splatter package
• added compatibility for Cellranger 3.0 10X files
• optional dependencies are now loaded at runtime
• scprep.plot.marker_plot now sorts markers and tissues by linkage by default
• bugfixes in multi-dataset histograms