Implement CSV export for ExportMultipleFiles tool

[bkis]

This PR implements a CSV export for the ExportMultipleFiles command line tool.
It uses the existing CsvExportPlugin, modified to use the existing default option values in case there is no Annotator instance running to pull option values from (which is the case in command line context).

There was also some code formatting done in CsvExportPlugin to maintain a more readable 100 char code width and tidy up some sprawling method calls.

Also, a mention of the stats option was added to the --help output of the ExportMultipleFiles tool, as it was missing but the export of stats seems to work fine. The info for qdtei is missing, too. But I cannot judge whether this one works as intended or is still a work-in-progress feature.

This would close #370.

[bkis]

The added commit (3174063) fixes the accepted input file names (for generating output file names from them) to include .ca2z files. A demo of the used RegEx can be seen here.