fixes enablement of layer move up/down actions

[fgdrf]

see issue #247

Now the selection is used to enable/disable Move Up/Down Action.

If there are Layers in between, that are not selected, it's possible to move up/down

As a result of Move Up the selection it would look like this:

Signed-off-by: Frank Gasdorf [email protected]

[fgdrf]

@egouge Is this interesting for SMART, isn't it?

[nprigour]

Nice improvement 👍 Why is it not yet integrated in the master branch?

[fgdrf]

@nprigour, Thanks!

I guess there is a little issue left. Assume the user has three selected layers such as

and clicks on the move down action. The first move is fine:

while the second mixes up the two lower once:

Not sure if it is really a bug but kind of confusing, isn't it?

[nprigour]

added a pull request to your local branch in relation to this. If you agree you can merge it and proceed with integration in master

[fgdrf]

I'm going to test your contribution. Thanks for collaboration! Appreciate your help here!