Allow multiple fields for dates

[jeremyboggs]

There are plenty of places in an item's metadata that can store dates. Additionally, the Dublin Core Extended plugin adds a variety of more granular date fields, all of which could be used to display an item on the timeline. Seems useful to add some way for users to choose multiple fields for Neatline Time to read for dates.

At its simplest, this could involve providing a way to do multiple selects for the Date field in the plugin options panel.