[DOXIASITETOOLS-85] moved RenderingContext from o.a.m.doxia.sink.render package to o.a.m.doxia.siterenderer


git-svn-id: https://svn.apache.org/repos/asf/maven/doxia/doxia-sitetools/trunk@1535929 13f79535-47bb-0310-9956-ffa450edef68