Regression: Output to stdout does not work anymore

[clementval]

Before the new driver, one could call clawfc without an output file or an output directory and the resulting transformed file would be output on the stdout. This does not work anymore:

Exception in thread "main" java.lang.Exception: Either output file or output dir must be specified
	at clawfc.Driver.verifyOutputDir(Driver.java:1619)
	at clawfc.Driver.verifyOptions(Driver.java:1746)
	at clawfc.Driver.run(Driver.java:90)
	at clawfc.Driver.main(Driver.java:67)