* 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
- added package option to specify which version of redmine
- added themes option back in to allow specifying redmine themes
- added plugins option back in to allow specifying redmine plugins
- added database.socket option to allow mysql unix socket authentication
- added port option to allow specifying the port rails runs on
- cleaned up Gemfile so it is much less hacky
- switched to ruby version 2.4 by default as suggested by documentation http://www.redmine.org/projects/redmine/wiki/redmineinstall#Installing-Redmine
- fixed an annoyance (bug) in the service causing recursive symlinks
- fixed ownership bug on log files generated by redmine
- updates reflecting renames in nixos options
- added a nixos test
