Embedding shader resources

[crud89]

Describe the pull request

This PR allows to embed shaders as binary resources into executables. For this, the CMake support for shaders has been extended. It is now possible to define one or more shader libraries, which translate to a header file for each library. Those can be included anywhere in the project. Shader modules can be added to a library, which results in a class to be created for them. The class name derives from the shader module name, where . and : characters are replaced by _.

A shader library header is private. If a shader resource should be made available to dependent projects (as in #54), a public interface granting access to the resource must be manually defined.

Shader modules can now be loaded from streams. The shader program builder API has been extended to support this, too.

As a result, the blitting compute shader required by the DirectX 12 backend is now embedded. This way, no manual copies are required for dependent projects for this shader.

Related issues

• Closes Allow loading shaders modules from streams. #41.
• Closes Allow shaders to be embedded into binaries. #49.