Add search path for shader files.

Helper: initShaderState(...) gets additional search path parameter.
ImportContext: Store an array of shaderSearchPaths.
Remove ShaderFactory (approach seems too complex)
Support default shaders with names.
SceneManagement: Use FileLocator for finding files.

ImporterTools: remove unused checkRelativePaths(...)
Use FileLocator for locating files where possible.

CoreNodeExporter: Don't change meshs' filenames when exporting.
CoreNodeImporter/CoreStateImporter/MeshImportHandler: Use FileLocator to locate files.
setRect(Geometry.Rec) function added
Compile fixes

MinSG::loadTexture ---> MinSG::createTextureState
modified
Adapt to changes in Rendering::Texture.
Merge branch 'master' of https://github.com/PADrend/MinSG
Add rendering layers.
physic modified
Adapt to changes in Texture.
Fix compile: createTextureState has been removed

API has been changed. Remove textures from tests to fix compilation.
Fix SoundEmittingBehaviour.
Create mipmaps for embedded textures (like for loaded textures).
Add ParticleReflectionAffector.
Remove unused code to get rid of warnings
ShaderState: Increase robustness when trying to use invalid shader.
Add renderingLayers parameter to collectVisibleNodes(...).
Merge branch 'master' of https://github.com/PADrend/MinSG