Made some fixes to find and test the right entities when checking whether to use default values. More work is needed.

Issue #1422600, Make sure end date cannot cause validation errors when show end date checkbox is not checked.

Issue #1417872, Remove code to compute missing date parts from empty values now that the new validation prevents that from working.

Make sure only new entities pick up default values, to avoid resetting an empty value to the current date.

Issue #1359464, Make sure that default values on hidden elements have the same construct as loaded values to avoid errors.

Fix to new default date handling, the default date has to set a date in the database timezone, not the display timezone.

Issue #1236216, Start the process of moving the repeating date integration out of the Date module and into a separate, Date Repeat Field module.

Issue #874322, The All Day functionality has been moved into a separate module and hooks were added to make it easier for other modules to inject steps into date processing.

 Issue #1363460, Make sure widget dates do not end up with the current date when they should be empty.

Issue #1266144, The end date should get set to blank if it is optional and matches the start date, but only if it is not populated by default values.

Issue #1349510, Make sure default values get populated before processing so they still get set on hidden fields.

Issue #1292898, Check for all day checkbox in the basic date element validation so empty time for newly added elements still passes validation.

Issue #1179715, Create a helper function for testing hidden/disabled dates and test each date element and validator to skip processing in that case.

Issue #1179715, When hidden by #access=FALSE, repeating date fields were getting removed and not replaced.

Issue #1179715, Don't do timezone adjustments in the widget, wait for #process so we can skip it when the date field has been hidden by #access.

Issue #1179716, Remove value_callback for date_repeat and date_combo forms, the default behavior works fine.

Issue #1178176, by das-peter, Fix date_combo_value_callback to return NULL to avoid data lost on untranslatable dates used with Entity Translation.

Issue #1257830, Beef up the logic when creating the date repeat tabs to work for more kinds of entities.

Issue #1216878, Re-introduce 'repeat' as a field setting rather than a widget type so people can't try to switch back and forth between repeating and non-repeating dates. Eliminate repeat widgets.

Issue #1243842, Make sure the All Day and Show End Date flags work correctly in unlimited value fields that use ajax.

Issue #1241576, Fix date combo validation for all-day dates so they don't fail validation because the format is unexpected.

Follow up to Issue #874322, Date popup field needs to accept date without time for the all day flag to work.

Issue #1234140 by arlinsundbulte, Change terminology in user-facing text from 'From/To Date' to 'Start/End Date'.

UI cleanup for the latest changes. All dates now need to be in fieldsets because of the additional floating checkboxes. Keep the from and to dates on separate lines rather than floating them (probably should make that an option). Added notes for themers about some of the changes.