Changed the load for the Shader and the shader itself to work properly.
Delete the created shader after they have been attached to the program. The Fragment shader has been fixed to work now.
Removed the init method from ShaderManager, as it was the only method used in the constructor.
Added a comment to the ShaderManager contructor.
Removed the unused constructor and destrcutor out of the ShaderLoader.
renamed the shader_id to program_id, as it's actually not a shader any more.
Added ModelViewProjection matrix into program. The matrix is used in the VS now.