Recurring jobs with HangFire

[odinserj]

Closes #62. Creating and running recurring job inside ASP.NET application is now as simple, as one line of code:

RecurringJob.AddOrUpdate(() => Console.WriteLine("This is awesome!"), Cron.Daily);

It uses the NCrontab library, so you can specify the schedule via CRON expressions:

RecurringJob.AddOrUpdate(() => Console.WriteLine("This is incredible!"), "0 12 * */2");

Recurring jobs are being created as regular background jobs, so you receive all other features of HangFire for free.

TODO:

• Finish the scheduler class, add tests.
• Add support for recurring job deletion.
• Display recurring jobs in HangFire Monitor.
• Handle JobLoadException
• Do something with recurring ids

[odinserj]