FCREPO-1161: Fix for SimpleDateFormat allocation in DateUtility
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 - switched to using the Joda Time implementation in DateUtility
 - DateTimeFormatter is thread-safe, so DateUtility can use static instances
 - Some differences in between diff chronologies have been accounted for
   in between Joda time and the Java API. (e.g. the long values for the 1/1/1 for
   java.util.Date and joda's DateTime is different. Therefore some test had to be changed
   please *check these*
 - I think i also fixed a bug in the test were XSD dates were used by tests for parsing
   Dates, but since these use 0000 as the year 1 BCE and joda time uses -0001 i had to change these.
   Please check that i did it correctly
 - fixed the values in DateUtility to use joda time's chronology