Move the inheritance logic to XMLFile class. Revert RenderPath class.

- Fix the original XMLFile used in the inheritance from being patched in the resource cache.
- Support multi-level inheritance.
- Support for all classes that use XMLFile for loading.
Code cleanup. [ci skip]
Fix for compiling in D3D9 mode on mingw-w64.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	Source/Engine/Resource/XMLFile.cpp