HBASE-23930 Shell should attempt to format `timestamp` attributes as ISO-8601
HBASE-23930 Shell should attempt to format `timestamp` attributes as ISO-8601

Make display of Cell timestamp be ISO8601 format instead of pure milliseconds.

mahak/hbase,ndimiduk/hbase,francisliu/hbase,apurtell/hbase,mahak/hbase,mahak/hbase,ndimiduk/hbase,Apache9/hbase,Apache9/hbase,mahak/hbase,ndimiduk/hbase,apurtell/hbase,apurtell/hbase,ndimiduk/hbase,apurtell/hbase,apurtell/hbase,Apache9/hbase,mahak/hbase,francisliu/hbase,ndimiduk/hbase,mahak/hbase,francisliu/hbase,Apache9/hbase,ndimiduk/hbase,apurtell/hbase,mahak/hbase,Apache9/hbase,apurtell/hbase,Apache9/hbase,apurtell/hbase,apurtell/hbase,mahak/hbase,francisliu/hbase,Apache9/hbase,francisliu/hbase,Apache9/hbase,Apache9/hbase,mahak/hbase,ndimiduk/hbase,francisliu/hbase,francisliu/hbase,francisliu/hbase,mahak/hbase,ndimiduk/hbase,ndimiduk/hbase,francisliu/hbase,ndimiduk/hbase,apurtell/hbase,francisliu/hbase,Apache9/hbase