date 6.x-2.0-rc6

- #341202, #339457, #337952, #329128, #337787, #341203, Fix repeating and multiple date displays.
- #273093 Add time formatter option to use in calendar views.
- #324063 Unset invalid values in the date argument position of the url to avoid various errors in the date argument handling.
- #301279 Remove README.txt for Date Popup, it's out of date and I'm moving documentation into the d.o handbook and Advanced Help.
- #337075 Change background-color:none to background-color:transparent.
- #324756 Bypass validation for empty, non-required dates.
- Fix broken Date API test broken by change in API.
- #340394 Fix four-digit year format for PostgreSQL.
- Fix bug in new date_field_get_sql_handler() helper function to pick up the right timezones for the handler.
- #338277 Make some improvements to datepicker css.
- #326722 Update the datepicker js to the latest version to fix bugs in current version.
- Date picker can't handle some year ranges that work in Date API, so adjust it as needed.
- #324150 Fix broken 'not between' date filter handling.
- #337784 Fix broken date filter to work correctly with the new year range values.
- #338237 Replace 'local_offset_field' with 'offset_field' in date handler.
- #338237 Fix broken date browser which never got updated to move date field info to $view->date_info.
- Make sure node edit form uses the right timezone for the database and field type.
- Fix logic error in date_convert when using timestamp with timezone other than UTC.
- #336255 Fix a few remaining places where timezone=none was not being handled correctly, and add update to clean up incorrect values stored in database.
- Eliminate date_timezone_convert() which wasn't working correctly to adjust dates without timezones and get rid of hard-coded 'UTC' for database values in favor of consistently using date_get_timezone_db().
- Date sql handler wasn't properly setting db timezone to UTC for mysql databases.
- Add a helper function date_field_default_values() that can be used to create new date fields in profiles and custom code.
- Add better separation to multiple date fields in the view admin summaries for date arguments and filters.
- #337764 Date filter wasn't correctly setting view date info, and also needs a year limit.
- #337301 Add hook_schema_alter to record addition of timezone_name to users table.
- #336255 Add new helper functions to make work of other modules, like Signup, easier. One helper to create a date handler for a field and another to do make date math easier.