Dump job and write service refactor

[thatbudakguy]

This attempts to extract the logic in common between GenerateFullDumpJob and GenerateDeltaDumpJob. It also pushes some of that logic onto the writer services MarcRecordWriterService and OaiMarcRecordWriterService, and attempts to have the latter manage its own files.

There are some placeholders for tests of the OaiMarcRecordWriterService; right now tests are failing because something's wrong with the logic to manage files. Everything else should be working.