* Added MediaType constants for the most common media types.
* Added a builder for ContentType objects.
* Added a method to SOAPVersion that allows to determine the media type used by a given SOAP version.


git-svn-id: https://svn.apache.org/repos/asf/webservices/axiom/trunk@1510114 13f79535-47bb-0310-9956-ffa450edef68