Moved the responsibility for finding file to load on to the ReaderWriter plugins,

instead of osgDB::Registry where it original lay.  This has been done to allow
fileName strings to be encode data rather than just file names, such as one
requires when using PagedLOD along with plugins for doing dynamic tesselation.

src/osgPlugins/txp/ReaderWriterTXP.cpp

@@ -21,7 +21,7 @@ osgDB::ReaderWriter::ReadResult ReaderWriterTXP::readNode(const std::string& fil
     if( !acceptsExtension(osgDB::getFileExtension(fileName) ))
         return ReadResult::FILE_NOT_HANDLED;
 
-	osg::ref_ptr<txp::TerrapageNode> pager = new TerrapageNode;
+    osg::ref_ptr<txp::TerrapageNode> pager = new TerrapageNode;
 
     pager->setDatabaseName(fileName);