Add datetime picker

This request should fix #157. It replaces the normal [JQuery Datepicker](http://jqueryui.com/datepicker/) with a [timepicker](https://github.com/trentrichardson/jQuery-Timepicker-Addon) courtesy of Trent Richardson, provided under an MIT license. 

To satisfy backwards compatibility concerns, by default or if the time selected is 00:00, the timepicker addon will not output a time to a "date" type metadata textbox. It will only output the time once a user has selected a time. Also, a datepicker is still utilized for the budget, so .date-time-pick and .date-pick classes have been created to differentiate between the two.

There are a [few areas](https://github.com/danielbachhuber/Edit-Flow/blob/master/modules/editorial-metadata/editorial-metadata.php#L706) in the editorial metadata module where a date is displayed using the default 'date_format.' (In the calendar, budget and posts table screen when the metadata is viewable). For stylistic purposes I left those as is, but they can be altered if it makes more sense to display the time in those areas as well.