AXIOM-418: Removed MessagingException from the methods in the FileAccessor API. Note that in some rare cases, this will break source code compatibility, but it will not break binary compatibility.

git-svn-id: https://svn.apache.org/repos/asf/webservices/axiom/trunk@1508538 13f79535-47bb-0310-9956-ffa450edef68