Profpatsch 488f0d9cb3 systemd-unit-options: startAt can be a list
OnCalendar entrys can be specified multiple times in a systemd timer, to
make more complex scheduling possible.

Tested by manually checking the timer generated by the following:

    systemd = {
      services.huhu = {
        description = "meh";
        wantedBy = [ "default.target" ];
        serviceConfig.ExecStart = "/bin/sh -c 'printf HUHU!'";
        startAt = [ "*:*:0/30" "*:0/1:15" ];
      };
    };

It prints HUHU to the log at seconds 0, 15 and 30 of each minute.
2016-09-01 00:39:36 +02:00
..
2016-08-28 13:33:13 +01:00
2014-07-30 16:19:26 +02:00
2014-02-08 14:59:52 +01:00
2014-07-30 16:19:26 +02:00