Prepare `v2.9.0`. (BlueBrain#924)

Version 2.8.0 (BlueBrain#836)

Co-authored-by: Luc Grosheintz <[email protected]>

Prepare version 2.7.1. (BlueBrain#712)

Prepare v2.7.0 (BlueBrain#696)

Update the change log and version number.

Prepare to release fixed build instructions. (BlueBrain#645)

Fix version in `CMakeLists.txt`. (BlueBrain#642)

Update changelog for v2.6.0 (BlueBrain#641)

Update changelog for 2.5.1 (BlueBrain#639)

Version 2.5.0 (BlueBrain#630)

Prepare `v2.4.1`. (BlueBrain#579)