Add feature that shows next estimated cron executions

[Marak]

This is already added, but commented out.

There are a few edge cases regarding bad cron formats / cron formats far into the future that were causing the functionality to not work well, so it was commented out. The dependencies and code are still included in the comments.

+50 Internet Points

[Marak]

https://github.com/harrisiirak/cron-parser looks like a nice alternate to using entire node-cron library.