Add two new parameters to the OAI harvester: timeout, combineRecords

The former is obvious.

The latter parameter allows administrators to tell the harvester to combine harvested records into
one collection file instead of one file per record. The harvester will combine these records after
every chunk (i.e., for every resumptionToken), therefore if a server's chunk size is set to 1000, then
instead of harvesting 3,123 record files, the harvester will create only 4 record files.
The default value is false.