I used plugin for eclipse. I think this one: http://sourceforge.net/projects/eclipse-rbe/
It is OK, allows adding and renaming properties, shows warnings if property is not translated to all supported languages etc.
Its disadvantage is that it always uses `\uXXXX’ notation for unicode characters. So, you must use this plugin to read created files. It makes search very hard. And I do not know whether it is possible to configure it to create UTF-8 encoded bundles.