Subject of the issue

Create the 1.6.0 release, the first release since August 18th, 2018.

Since it has been so long, the maintainers have decided to create a pre-release (1.6.0.pre1) with the pending changes. The maintainers will need to determine criteria for releasing a proper 1.6.0 release and put it in this issue so that people will know what to expect.