Upgrade to Joda-Time 2.9.4

See http://www.joda.org/joda-time/upgradeto294.html

Changes in 2.9.4
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• DateTimeZone data updated to version 2016d
• Loading time-zone provider now occurs in a priveleged block 327, #375

Changes in 2.9.3
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• DateTimeZone data updated to version 2016c
• Make DateTimeUtils.SYSTEM_MILLIS_PROVIDER public 357
• Fix bug when adding months at the maximum limits of integer 361
• Add Turkish period translations 364