Bug fix for bug #197

Root cause was that the `BackupFileRotation` did not delete the oldest backup which results in this error as the maximum number of backups, as specified by `numberOfMetaBackups` in `goobi_config.properties`, had been created. In addition, when running on Windows, the metadata editor hung loading infinitely because the renameFile() method didn’t check if the destination file exists and mistakenly waited that Windows would release a lock on that file because the wait timeout was never reached due to a missing counter increment. After fixing the counter increment, a non-translating error message was showing:
> fehlerNichtSpeicherbar (IOException): Renaming of […]/temporary_meta.xml into […]/meta.xml failed.

##### Changes:
- Added deleting of the oldest backup
- Made renameFile() check if destination exists and fail immediately in that case
- Removed hiding catching of IOException
- Added counter increment
- Fixed translation for error message