Disable mutiple collection in the field harvesters.collections

• The database field collections harvesters.collections can contain several collections separated by a comma,e.g. LHCb Papers, LHCb Detector Performance Papers
• This behavior is not compatible with collection defined using author name, e.g. find a nguyen, v g.
• Modify the logic to one harvesters one collection
• Create a script fixHarvestersCollections.py to fix multiple cds collections.