Added help for time/date template specifiers

rtdata/languages/default

@@ -2121,6 +2121,8 @@ QUEUE_LOCATION_TEMPLATE_HELP_RANK_TITLE;Rank
 QUEUE_LOCATION_TEMPLATE_HELP_RANK_BODY;<b>%r</b> will be replaced by the photo's rank. If the photo is unranked, '<i>0</i>' is used. If the photo is in the trash, '<i>x</i>' is used.
 QUEUE_LOCATION_TEMPLATE_HELP_SEQUENCE_TITLE;Position/sequence in queue
 QUEUE_LOCATION_TEMPLATE_HELP_SEQUENCE_BODY;<b>%s1</b>, ..., <b>%s9</b> will be replaced by the photo's initial position in the queue at the time the queue is started. The number specifies the padding, e.g. <b>%s3</b> results in '<i>001</i>'.
+QUEUE_LOCATION_TEMPLATE_HELP_TIMESTAMP_TITLE;Date and time
+QUEUE_LOCATION_TEMPLATE_HELP_TIMESTAMP_BODY;Three different date/time values may be used in templates:\n  <b>%tE"%Y-%m-%d"</b> = when export started\n  <b>%tF"%Y-%m-%d"</b> = when file was last saved\n  <b>%tP"%Y-%m-%d"</b> = when photo was taken\nThe quoted string defines the format of the resulting date and/or time. The format string <b>%tF"%Y-%m-%d"</b> is just one example. The string can use all conversion specifiers defined for the g_date_time_format function (see https://docs.gtk.org/glib/method.DateTime.format.html).\n\nExample format strings:
 QUEUE_LOCATION_TEMPLATE_HELP_EXAMPLES_TITLE;Common examples
 QUEUE_LOCATION_TEMPLATE_HELP_EXAMPLES_BODY;If you want to save the output image alongside the source image, write:\n<b>%p1/%f</b>\n\nIf you want to save the output image in a folder named '<i>converted</i>' located in the source photo's folder, write:\n<b>%p1/converted/%f</b>\n\nIf you want to save the output image in\n'<i>/home/tom/photos/converted/2010-10-31</i>', write:\n<b>%p-3/converted/%P-4/%f</b>
 QUEUE_LOCATION_TITLE;Output Location