ImageData:encode now supports saving exr image files.

Also add support for loading uint exr image files, and fix a memory leak in the exr loading code.

Resolves #1813.

src/modules/image/FormatHandler.h

@@ -43,6 +43,7 @@ public:
 	{
 		ENCODED_TGA,
 		ENCODED_PNG,
+		ENCODED_EXR,
 		ENCODED_MAX_ENUM
 	};
 
@@ -116,6 +117,11 @@ public:
 	 **/
 	virtual void freeRawPixels(unsigned char *mem);
 
+	/**
+	 * Frees encoded image memory allocated by the format handler.
+	 **/
+	virtual void freeEncodedImage(unsigned char *mem);
+
 }; // FormatHandler
 
 } // image