Start on coding "subscenes", i.e. a tree structure of scene-like structures.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rgl@1001 79a1b648-8b68-254f-b20b-c0b50f5137bf
typo

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rgl@1002 79a1b648-8b68-254f-b20b-c0b50f5137bf
Port r1002 from trunk

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/rgl@1003 79a1b648-8b68-254f-b20b-c0b50f5137bf