* redmine: 3.4.8 -> 4.0.1
* nixos/redmine: update nixos test to run against both redmine 3.x and 4.x series
* nixos/redmine: default new installs from 19.03 onward to redmine 4.x series, while keeping existing installs on redmine 3.x series
* nixos/redmine: add comment about default redmine package to 19.03 release notes
* redmine: add aandersea as a maintainer