String getParamOutContent(String... params) throws Exception {
        resetContent();
        TikaCLI.main(params);
        return outContent.toString("UTF-8");
    }
reset outContent and errContent if they are not empty
run given params in TikaCLI and return outContent String with UTF-8
tika-app/src/test/java/org/apache/tika/cli/TikaCLITest.java