Bitarchive dirs need to be used in a row

If you have more than one directory for storing arc files, you can add all directories under <bitarchive><baseFileDir> in the settings.xml. Each directory is a baseFileDir Entry under bitarchive.
If a directory doesn't provide enough diskspace the next directory will be taken. It is expected - and in our case it is mandatory - that the order of directory will be taken from entries under the bitarchive tag in settings.xml. The direcories should be used in the same row.
Actually the direcories will be read in the correct order but later in the BitarchiveAdmin class, these entries will be put in a HashMap. And this class doesn not guarantee that the order will remain constant over time. So that order which is giving back might be correct or not.