PDFBOX-1915: backport shading changes from the trunk done in GSoC2014 by Shaola Ren to the 1.8 branch

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/branches/1.8@1617131 13f79535-47bb-0310-9956-ffa450edef68
PDFBOX-1915: reformatted the package

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/branches/1.8@1617132 13f79535-47bb-0310-9956-ffa450edef68