OSGDB_EXPORT macro to RegisterCompressorProxy, and modified the
findCompressor() method to look for custom compressors in libraries
such like osgdb_compressor_name.so, which was described in the wiki
page chapter 2.4."
to the osgDB::Registry. Added a osgDB::Registry::getObjectWrapperManager() for access of this object wrapper manager. This
change centralises the singleton management in osgDB.
Merged the osgDB::GlobalLookUpTable functionality into ObjectWrapperManger to keep down the number of singletons in use.
From Robert Osfield, refactor of Wang Rui's original osg2 into 3 parts - parts placed into osgDB, the ReaderWriter placed into src/osg/Plugin/osg and wrappers into src/osgWrappers/serializers/osg