To make it easier/possible to write stable unit test the CSV upload
can optionally wait until all entries have been flushed to disk.
This is necessary for tests that ingest data and then read the data.
Refactoring to prepare the addition of CSV parsing rules. The parsing
rules will contain information about which columns to ingest or ignore.
This will be used to add the ability to upload files via HTTP post in
addition to the TcpIngestor.