job level dependency and email notification

[winghc]

here we change the code and add the below features:

1. job level dependency: When one job A is finished, one token which composed by job_name and date_flag will be persisted in db, the jobs which run depend on job A's status can check this token and consume it.
2. email notification: for cron job, once it finish for one cycle, can send out notification email, so we know it's daily status.

later on, we will publish our changes for your review and merge if you need.

[tobwiens]

Very good, submit it as a pull request and we will go through the changes.

Do you mind telling us more about the use case? Is that an email notification for all sorts of tasks?