User would like to open and edit assets

As part of the UI creation workflow, user wants now and then to edit the content of the assets. We should have a way in QDS to open the file for editing, like.

1. see "_4kICE" as image in property editor
2. right-click and open context menu where you have
   1. "Open with..."
   2. or open the native file explorer (explorer, finder, etc)
3. user edits the file (e.g. with photoshop)
4. user saves the changed file with
5. project is updated on QDS

Applies to all assets (anything that is not std. qml)

We can also have user definable tools (or save the used preset?) so that if user wants to edit e.g. shader they don't need to go thru file view each t ime