Suggestion for log4j.xml example inside preflight source

As posted by rnibali to the mailing list:

I recently ran some tests using the preflight core, and wondered about the
following message:

java -jar preflight-app/target/preflight-app-2.0.0-SNAPSHOT.jar xml batch
./OpenSource/pdftests/
log4j:WARN No appenders could be found for logger
(org.apache.pdfbox.pdfparser.COSParser).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for
more info.

The online PDFBox FAQ (kind of) told me how to solve this. However, using
the example log4j.xml from PDFBox yields the following:

java -Dlog4j.configuration=file:./preflight/src/test/resources/log4j.xml
-jar preflight-app/target/preflight-app-2.0.0-SNAPSHOT.jar xml batch
./OpenSource/pdftests/

log4j:ERROR No appender named [console] could be found.
log4j:ERROR No appender named [rolling-file] could be found.

My suggestion is to replace it with this for starters:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration debug="true" xmlns:log4j='http://jakarta.apache.org/log4j/'>
        <appender name="console" class="org.apache.log4j.ConsoleAppender">
            <layout class="org.apache.log4j.PatternLayout">
                <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
            </layout>
        </appender>
        <root>
                <level value="DEBUG" />
                <appender-ref ref="console" />
        </root>
</log4j:configuration>

Additionally, the FAQ entries should be updated with a correct example
regarding the 'java -jar ..." case.