storage of the path lists into osgDB::Registry, and changed the data
structor from a char* to a std::deque. Changed a names of couple of the
convinience functions in osgDB/FileUtils to better reflect the two
public FilePathList's - DataFilePathList and the LibraryFilePathList.
Added support into the osgDB::Registry::readNode/Image/Object methods
for pushing and popping the path of the current file being loaded.
for settings options in osgDB::Registry, and added the paramter to all of the
reaader/writer plugins. The Options structure by default has an string attached
for packing basic options, however, it also can be subclassed to encapsulate
any users defined option data. In the later case both the client code *and*
the plugin need to be aware of subclass, the plugin will need to use
dynamic_cast<> to assertain its type.
