ENH: more detail in debug messages in date/time detection
ENH: add date format 2005-01-23 21:59:59 (%Y-%m-%d %H:%M:%S) so ISO8601 doesnt handle it
ENH: iso8601 - remove default_timezone set to UTC, isn't valid any more - calculate from local timezone. Enforce T date/time separator in iso8601 regex. Make minutes in timezone optional as per ISO8601. Use consistant regex for ISO8601