New Option Type: Date

# Output Screenshot: 
![171caf11b68e0495431234b072a15d3cdcc5da29e7](https://cloud.githubusercontent.com/assets/6664406/4710892/ac4d5274-58b0-11e4-882d-c259c22d5b64.png)

# Input Screenshot: 
![](http://new.tinygrab.com/171caf11b6420210e834e0b30bd9d9c0a2dcd4186a.png)


# Notes:
- I didn't have time to make it work within theme customizer, but it
shouldn't be difficult to add.
- Kept it as simple as possible
- JS Libraries used: jQuery UI Datepicker (included in WP) and a
Timepicker add-on for it (
http://trentrichardson.com/examples/timepicker , https://github.com/trentrichardson/jQuery-Timepicker-Addon )