Moved Registry::ReadFileCallback + WriteFileCallback, and osgDB::ReaderWriter::Options into their own separate Options file and into the osgDB namespace.

Introduced a new callback osgDB::FindFileCallback that overrides the default behavior of findDataFile/findLibraryFile.

Introduced support for assigning ReaderWriter::Options directory to PagedLOD.

Introduced new osgDB::FileLocationCallback for assistancing the DatabasePager to know when a file is hosted on a local or remote file system.

src/osgDB/FileCache.cpp

@@ -30,6 +30,11 @@ FileCache::~FileCache()
     osg::notify(osg::INFO)<<"Destructed FileCache "<<std::endl;
 }
 
+bool FileCache::isFileAppropriateForFileCache(const std::string& originalFileName) const
+{
+    return osgDB::containsServerAddress(originalFileName);
+}
+
 std::string FileCache::createCacheFileName(const std::string& originalFileName) const
 {
     std::string cacheFileName = _fileCachePath + "/" +