This adds a date range search option to partial sending. I'd like to add these partial sending search stuff to just search an actual list, rather than just using it here. 

The date picker stuff also has to loaded only when it needs to be used.
date range works with Beatitude, I think... datetimepicker only loaded when needed. Don't Send, archive now uses data picker, what else?
Adding explicit partial_listing in the search_list method
Tweaks to make this form a little more reusable?
And now, we have an extremely rough advanced search.