Get transcripts in other formats than ISO/TEI

[berndmoos]

It is useful to be able to get transcripts in EXB, EAF, FLK and possibly other formats.
This is sort of already done in the download part of the ZumultServlet, but this is not the right place.
The default way can be to convert from ISO/TEI to the desired format.
However, there may be cases where

1. The desired transcript already sits on the server
2. The version that sits on the server is not what comes out of the conversion (e.g. because it was the source of a transformation to ISO/TEI, but information such as tokenisation was added)

So, I'm trying to add a method getTranscript(String transcriptID, TranscriptFormat transcriptFormat) to BackendInterface. AbstractBackend can implement this by returning a converted transcript (or ignoring the transcriptFormat parameter?). Other backends can override this method to get the transcript stored in the backend.

This is complicated, so I'm doing it in a new branch...

[berndmoos]

Maybe not too complicated... Added the method to the backend, implemented it in AbstractBackend (where it does nothing for now), overrode it in COMAFileSystem backend, where it will look for an EXB file with the same name as the ISO/TEI file and extension .exb and then initialise a new Class EXBTranscript with that XML.

To do: see which methods can be meaningfully implemented for EXBTranscript (several methods in the Transcript interface only make sense for ISO/TEI transcripts)