Add xdan-datetimepicker-rails and datetime_picker input
Rename to combined_date_time_picker, add specs
Fix the broken datepicker and combined_date_time_picker specs
Add docs for combined date-time picker
Properly add datetimepicker to its fields

This will now go through the page and find all fields
which will use the combined date-time picker and set them up
on page load. It will also go through and find relevant fields
to set up whenever a has_many field is added.