Edit menu > reorder Cut/Copy/Paste variants

I've debated this change for some time, and while this new menu order
deviates from Photoshop, GIMP, etc, I think it is the right choice.

Photoshop et al make their stock Cut/Copy/Paste actions default to
operating on the current layer.  Special options are provided for
image-level variants (e.g. "Copy Merged" to operate on the full image
instead of just the active layer).

This behavior is confusing to new users, as I have discovered from bug
reports claiming that "PhotoDemon's Copy command doesn't work", when the
user has simply created a selection that doesn't overlap the active
layer (so the copy command has copied a fully transparent region to the
clipboard).  Thus, I believe that Cut and Copy should Cut and Copy the
*image as it appears on-screen*, e.g. the full layer stack instead of
just the active layer.  This is the most intuitive behavior, especially
as "copy from layer" may copy an image completely different from the
on-screen appearance (as variable opacity and blend mode will not be
processed by the command, per convention).

As such, I have reworked PD's menu so that Cut and Copy default to
operating on the image as a whole (e.g. Copy actually implements a Copy
Merged action).  The Edit menu thus reads:

Cut
Cut from layer
Copy
Copy from layer

Using this logic, consistency dictates that the default Paste command
should also operate at an *image level*, not a *layer level*, so Ctrl+V
now maps to "Paste as new image" instead of "Paste as new layer", and I
have swapped the position of these two commands in the Edit menu.

Finally, note that "Cut from image" is not provided by any other photo
editor (to my knowledge), but I feel it necessary to provide such an
option, despite its inherent complexity.  I believe in always adhering
to a rule of symmetry with PD menu options - e.g. if there is an option
to blur, there should be an option to sharpen.  Similarly, if Copy
provides two variants (Copy Image and Copy Layer), Cut should do the
same, as it should be identical in behavior to Copy, but with the added
final step of erasing the region when we're done copying it.

Anyway, I probably over-thought this (like most PD things, ha), but I
think the new menu order is the least of all evils, especially for new
users.
Edit > Cut (from image): implemented