Add column holding the filename of last file used for updating reporter annotations

[Nicklas Nordborg]

This is to simple let everyone know where the annotations are coming from. This should be added as a string column on a similar footing as the 'lastUpdate' column. Plug-ins must of course let the core know about the filename, so it can only be made semi-automatic. A possible (and easy) way is to create a ReporterBatcher.setFilename() method. Plug-ins should call this method to automatically let the core set the filename. Null is an allowed value. Should the core reset the value if a plug-in never calls the method or should it be left unchanged? What if a reporter is manually updated from the web interface? Maybe we could store the name of the user in this case?

Note that the column should only hold the filename. It is not a reference to a file on the BASE file system, because foreign keys in the reporter table are only good for decreasing performance.

NOTE! Do not forget to update the UML diagrams and documentation!