Adding dot OSG support to allow osgDB::writeObjectFile(osg::Array,...) to function as expected. This involves creating a new plugin osgdb__osgobjects, and we force it to load at init time in osgwTools/PluginLoader.cpp

git-svn-id: http://osgworks.googlecode.com/svn/trunk@489 c67418bc-a6eb-11de-8ba5-91705c1537ed