Release 6.20.0: Setting log properties as default

[changerequest]

Due to a Professional Services request, use ful log properties are set as default in file server.properties:

com.openexchange.log.propertyNames=com.openexchang e.ajp13.remoteAddress(ERROR),com.openexchange.sess ion.userId(DEBUG),com.openexchange.session.context Id(DEBUG)