Fix bulk importer's metadata.properties character encoding

• Using bulk importer, import data with a metadata.properties file containing:

  dc\:description=Héhéhé hoùoùoù hàààà 緊急地震速報や豪雨予報をいち早くお知らせ {test} '"

• Result:

  Héhéhé hoùoùoù hà à à à  ç- Šæ€¥åœ°éœ‡é€Ÿå ±ã‚„è±ªé›¨äºˆå ±ã‚’いち早くお知らせ {test} '\"

=> accents and special characters should be properly encoded