Need instructions for localising bundled plugins for JIRA 4.0

In earlier versions of JIRA, localising plugins was more straightforward. These days, it's not clear, for example that the dashboard needs to be translated by adding properties files to various jar files in the bundled plugins zip file.

We could generate a list of all the i18n files during the build and maybe create a readme or something which is referenced by some documentation for localising JIRA.