regedit: Remove windows class names (they shouldn't be localized) and unused IDC_REGEDIT menu from resources.

Add a test to make sure the saved image has the same dimensions as
original. Delete the test file when finished.

Implement the encoding function for GDI+ images so that
GdipSaveImageToStream can encode images as BMP files.

Add the correct framework for a fully-functional implementation of
image encoding (not a hack like before). Currently, only a stub for
BMP encoding is supported. New tests added as well.

Still need to implement saving the image based on the encoder
parameter.
Basic tests included.