Add function to calculate a camera frustum.
- fixed shader bug for output normal
- moved video3d shader code to resources
- removed obsolete resources
Remove unnecessary NodeVisitor.cpp file.
Simplify child traversal.
Add dfs_traverse function.
Add dfs_traverse_if
Merge branch 'feature/traverse' into develop
Merge pull request #33 from scholli/develop

Develop
Use iosfwd with forward declarations.
Remove unneeded include.
Fix return types.

Temporary values should be returned by value in C++11.
-rename classes that hold ressources
- renamed implementation of ressource classes
fixed typo in Database.hpp
merge
slightly improved da thing (at least it doesn't crash anymore)
- renaming of classes and filenames according to new ressource/node/shader scheme
- working separation between different geometry types
- issing features :
  + shadow map ubershader
  + textured quad, ray and bbox drawing
- Added GeometryUberShader base class