Template to display the Views date filter form.
Values available vary depending on the operator. The availability
of date vs adjustment depending on the filter settings. It can
be date-only, date and adjustment, or adjustment only.
If the operator is anything but 'Is between' or 'Is not between',
a single date and adjustment field is available.
If the operator is 'Is between' or 'Is not between',
two date and adjustment fields are available.
A description field is also available.