First part of render texture commit

Added NzContext::EnsureContext and NzContext::GetThreadContext
Added NzCube
Added NzRect::GetCenter
Added methods to send vectors to shaders
Added NzRenderer::SetViewport
Fixed NzRect::ExtendTo calculations
Fixed NzImage::Update checks with level > 0
No longer use glTexStorage when creating a texture to prevent a bug
NzBuffer's Lock and Unlock operations renamed to Map and Unmap
NzVector2/3/4 can now cast implicitly to a pointer
Optimized compilation time of String.hpp
Optimized normalisaton of quaternions
Optimized passing uniforms to shaders
Quaternion now automaticaly Normalize h
Removed macro definition of NAZARA_RENDERER_OPENGL from Renderer
Removed implicit cast from NzVector2/3/4 to NzString
Renamed nzBufferLock to nzBufferAccess
Renamed NzRenderTarget::CanActivate to IsValid

include/Nazara/Renderer/RenderTarget.hpp

@@ -21,15 +21,16 @@ class NAZARA_API NzRenderTarget
 		NzRenderTarget() = default;
 		virtual ~NzRenderTarget();
 
-		virtual bool CanActivate() const = 0;
-
-		virtual NzRenderTargetParameters GetRenderTargetParameters() const = 0;
-
-		#ifdef NAZARA_RENDERER_OPENGL
+		#ifndef NAZARA_RENDERER_COMMON
 		virtual bool HasContext() const = 0;
 		#endif
 
+		virtual unsigned int GetHeight() const = 0;
+		virtual NzRenderTargetParameters GetParameters() const = 0;
+		virtual unsigned int GetWidth() const = 0;
+
 		bool IsActive() const;
+		virtual bool IsValid() const = 0;
 
 		bool SetActive(bool active);