Installations which were using early versions of the dashboard editor, which was first available
our nightly builds from 2014-08 till 2014-10 and created dashoards with it, have now dashboards
saved in a format, which can not be interpreted by the current dashboard code.
For some time, we assumed that there were not many installations with such files, therefor we
did not implement any migration code and asked the users to migrate by hand. But now we have
a bit too many users which are having trouble here, so we decided to implement a migration
routine for these dashboards.