Catch broken configurations inside of the Post Processing shaders.

This catches most instances of configuration failures that can happen in a post processing shader.
Gives a user a helpful error message that lets them know what they have failed to set up correctly

Source/Core/VideoCommon/PostProcessing.h

@@ -21,6 +21,7 @@ public:
 			OPTION_BOOL = 0,
 			OPTION_FLOAT,
 			OPTION_INTEGER,
+			OPTION_INVALID,
 		};
 
 		bool m_bool_value;
@@ -75,6 +76,9 @@ private:
 	std::string m_current_shader;
 	ConfigMap m_options;
 
+	// Verifies if a configurationOption is valid or not
+	// Returns an error string on error
+	std::string VerifyOptions(const ConfigMap& config_map);
 	void LoadOptions(const std::string& code);
 	void LoadOptionsConfiguration();
 };