Added method for escaping double-quoted strings.
Removed unnecessary @SuppressWarnings("unchecked")
Added 2 test utilities.

GetDocFromContentStore retrieves whole documents from the content store.
GetFieldValues determines what values metadata fields can have.
Slight change to Sonar CMDI metadata fetcher.

This class functions as an example of an external metadata fetcher;
eventually we will put this in a separate project and provide a more
generic metadata fetcher as an example.