Add function to calculate a camera frustum.
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.
fixed typo in Database.hpp
merge
- Added GeometryUberShader base class
- UberShader for various geometries now derived from GeometryUberShader
- added support for textured quad node for new rendering interface
- clean up rendering with new interface
- working primitives
- to test: shadows
removed geometry dependent interface from ubershader and moved to geometryubershader
- minor fixes
Merge branch 'develop' of https://github.com/vrsys/guacamole into develop

Conflicts:
	src/gua/renderer/Pipeline.cpp
	src/gua/renderer/Serializer.cpp
- removed win32-preprocessor code for msvc_version < msvc12