NEST 2.20.2

NEST 2.20.2 is the result of 15 commits by 7 developers since NEST 2.20.1 which was released on 2020-12-02.

This release contains mainly bug fixes and backports. Most notably it brings support for detailed timers (#2086, which allows more consistent comparisons between benchmark results obtained with this and later versions.

In particular it contains

• Add standard and detailed timers for benchmarking purposes for NEST 2.20.2
• Backport documentation for built-in and detailed timers
• Update NEST 2.20.x CMake configuration to support OpenMP fully on OSX
• Revise NEST 2.20.x guide on random numbers to be ajour with NEST 2.12 and later