Changed scheduleJob method signature to take when parameter first

no issue

- Accepting the schedule or a data when scheduled job should be run would follow a signature used in other established frameworks: (1) https://github.com/mperham/sidekiq/wiki/Ent-Periodic-Jobs#definition
- Another reason to put scheduling parameter first is this would allow leaving an optional "data" parameter as last

ghost/job-manager/lib/job-manager.js

@@ -44,11 +44,11 @@ class JobManager {
     /**
      * Schedules recuring job
      *
-     * @param {Function|String} job - function or path to a file defining a job
-     * @param {Object} data - data to be passed into the joba
      * @param {String} when - cron or human readable schedule format
+     * @param {Function|String} job - function or path to a file defining a job
+     * @param {Object} data - data to be passed into the job
      */
-    scheduleJob(job, data, when) {
+    scheduleJob(when, job, data) {
         let schedule;
 
         schedule = later.parse.text(when);

ghost/job-manager/test/job-manager.test.js

@@ -17,7 +17,7 @@ describe('Job Manager', function () {
             const jobManager = new JobManager();
 
             try {
-                jobManager.scheduleJob(() => {}, {}, 'invalid expression');
+                jobManager.scheduleJob('invalid expression', () => {}, {});
             } catch (err) {
                 err.message.should.equal('Invalid schedule format');
             }