Change Clipboard Mime-Type to Support Text

[indianajson]

Proposal to update Clipboard mime-type to text/plain to allow for interoperability of copy/paste functions with external programs. Please see Issue 4290 for details.

[bjorn]

There's a few downsides to this approach:

• The Paste actions will get enabled when there is any text in the clipboard (though they silently fail when triggered).

• It breaks compatibility with older versions of Tiled (though it'd be rather unlikely for somebody to be copy/pasting stuff between two different versions of Tiled).

• If people copy any TMX file to their clipboard, trying to paste it will yield a rather broken thing because Tiled will not be able to resolve any of the tileset or image references (this may the most serious issue). To make this work, Tiled copies TMX in a special mode that forces all external references to use absolute paths.

So first I'd like to know whether it's really not possible to just use the text/tmx mime-type.