tools (common/date_utils): date_parse_ext + timezone handling: - new date_parse_ext method parse a date where relative informations can be added. e.g.: "1 week ago", "now - 2 days", "01/01/01 01:01 + 3 hours". - new TZ_UTC and TZ_LOCAL constants can be used to use UTC time or local time zone. - date_parse* can now use a default_tz, which will be used if timezone if not specified in date format (default UTC). - tz_info can now be used in date_format to format the time in given timezone (default: UTC).