Add day, month and day of week option to cron job.

[bschonec]

Added day of month, month and day of week options to the AIDE cron job. In my environment, running the AIDE job every day was taxing my servers too much. Once a week or once a month is sufficient for my purposes.

Also, I simplified the cron.pp manifest a bit since all that logic was just to build the command variable for the cron job.

I have no idea how to update spec tests and am trying to learn how to do so. If someone can help add spec tests, I would be most appreciative.

[kekogya]

@bschonec, thank you for your contribution to this code base. I will merge your change and then work on updating the module on puppet forge in the next couple of days.