Editor: duplicate project items (Characters, GUIs, and so on)

[selmiak]

I noticed I wanted to clone a gui and change some minimal parameters, why is this not possible? You can export the gui to a *.guf file and reimport that one, but direct cloning seems a more common thing to do than exporting. Exporting is important too, but just cloning would be a nice feature to have. Just keep interating the gGUIname through gGUIname2, gGUIname3, etc.

I noticed this on GUIs, but I think a cloning function for characters, inventory items, and more with the exact same settings will be useful too.

[ivan-mogilko]

The task should be following:

1. Implement "Duplicate" or "Clone" context menu command for each eligible project item (see below).
2. The command should take the current item and create a shallow copy, that is copy only the item itself, but not the resources it uses or other items it references. The clone should just link to the same resources / items.
3. The copy is assigned the first free ID, and a unique name, preferably using existing method Factory.AGSEditor.GetFirstAvailableScriptName.

Eligible items:

• Character
• Cursor
• GUI
• InventoryItem
• View

Other possibilities:

• Dialogs: no idea if may be useful. Maybe cloning dialogs may be useful if there's a need to have repeating options, or other reasons. But then there's a question whether they should be copied with a script or not.
• Font: currently involves copying a font file, but see Fonts: allow font instancing with different properties #996 beforehand, maybe that should be done first.
• Scripts: probably not? easy to do by hand.
• Rooms: may be done by simply copying files?