Copy/Paste special for meshes and attachments

**From this Forum thread:**
http://esotericsoftware.com/forum/4-questions-about-functionality-13388

Provide a more straightforward way to copy a mesh configuration to another attachment directly.

**The desired operation is to have a "copy/paste special"** like in MS Office Word. We could choose to paste "position", "mesh config", "attachment path", "animation key", or even something more like color, etc.

> The current workflow for this is to clone the mesh attachment and replace the target attachment. However, by doing so, the step itself introduce quite some maintenance works:
> 1. Once cloned the attachment, original attachment became inactive, need to reactivate after moving.
> 2. The position is keeping the old value after dragging. Need to correct it after dragged to the new slot.
> 3. The attachment name has a number appended on it because during the cloning, the name cannot be the same under the same slot. This sometimes is confusing because the cloned plant2 attachment is actually pointing to plant1 and there could actually already be a plant2 image.

> (...) Especially after dragging the attachment to a new slot but the attachment is keep at the old slot position is the most not wanted side effect. It is not much work when only dealing with two or three slots but when when dealing with objects that has like 10~20 copies, the work become tedious.

> When you do plan to move it to another slot the renaming is unfortunate and would need a function that knows the desired slot, as you described with "paste special". Keeping vs not keeping the position when changing slots is an interesting idea.