Also removes configText, functionality is now provided more conveniently by configOptions.
Keep in mind that this breaks compatibility with previous configurations,
configFile provides a means to protect the CI token from being written into the nix store.
The current behavior was for gitlab-runner is to immediately terminate when there
was a restart required. This can lead to aborted builds and is annoying to users.
By enabling graceful mode gitlab-runner will wait for all builds to finish before
terminating. The disadvantage is that a nixos-rebuild switch needs to wait till
all jobs are done. Because of that it is not enabled by default.
