Merge branch 'master' into devel

* master:
  Version 0.99.15
  Remove dropout.present estimation
  Add limits to zeros plots
  Adjust default splat DE fac params
  Add BPPARAM to scDDSimulate
  Add summariseDiff function

From: Luke Zappia <lazappi@users.noreply.github.com>

git-svn-id: file:///home/git/hedgehog.fhcrc.org/bioconductor/trunk/madman/Rpacks/splatter@128698 bc3139a8-67e5-0310-9ffc-ced21a209358