Add specifyTimeChecked plugin option

This option allows the time support plugin to show the time picker
panel when initially rendered.
Set the time support panel visibility on render

The specifyTime plugin option ensures that the checkbox state can be
set when rendered.

This change ensures the time support panel visibility state
matches the checkbox.
Set time fields when specifyTimeChecked is true

When the date range picker is setup with the specifyTimeChecked
plugin option set to true, the time fields now show the calendar
time in UTC instead of 00:00 when opened.
Fix display mode when opening panel
Add start and end date for demo