Store an id counter for each entity type that uses a generic numbered key in DumpFileWriter.  This permits to use more then one search expression for the same type.
Store an id counter for each entity type that uses a generic numbered
key in DumpFileWriter.  This permits to use more then one search
expression for the same type.

git-svn-id: 5b1347ddac5aba1438c637217dfe0bb137609099@525 8efdbd46-c5fb-49ab-9956-99f62928ec21

icatproject/python-icat