Arq doc: Missing note about -Darquillian.xml=some-file-or-classpath-resource.xml

http://docs.jboss.org/arquillian/reference/latest/en-US/html_single/
4.4. Container configuration

Missing these information:

• the -Darquillian.xml=... sys prop
• that it can be a path on classpath or filesystem
• which of the above takes precedence