Supporting functionality added to date/time picker and progress dialog

Supporting functionality added to date/time picker and progress dialog

Here the date/time picker is given the ability to dynamically hide the time
picking component when show-time-picker is in effect.  This allows an
interface to use the time picker based on ephemeral state information and to
hide it when not useful.

Additionally, the progress dialog now takes an optional label property that
can be passed to both open() and update(), so that textual information can
be provided along with the numeric and visual progress data.

Signed-off-by: Mike Rylander <mrylander@gmail.com>