Revert to using java.text.SimpleDateFormat for retrieving timestamps

Millisecond parsing in Joda has different results than with Date/SimpleDateFormat.  If the number of ms digits in the format string exceeds the number of ms digits in the date string, then zero padding happens on the wrong side (e.g. 93 becomes 930 instead of 093).  If the number of ms digits in the date string exceeds the number of ms digits in the format string, then parsing fails.

See https://github.com/JodaOrg/joda-time/issues/62.

Fixes http://trac.openmicroscopy.org/ome/ticket/12117.