SLING-3175 - Make MediaRange parser linient to accept invalid Accept header generated by Oracle JDK HttpUrlConnection

Relaxing the parsing logic for type/subtype to allow handling of header like
`text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2`

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1541131 13f79535-47bb-0310-9956-ffa450edef68