Option to change the shortcut Ctrl+C between copy and copy picture data

[shioku]

Problem
If you want to copy a picture to a website which supports upload of pictures like the editor on github with the "normal" copy (Ctrl+C) nothing will happen. You have to copy the picture data for it to work. Which is at the moment a fixed shortcut which can't be changed. (Ctrl+Shift+C)

Solution
A setting with a simple checkbox to be able to change the behavior between the two copy shortcuts.
So everyone can decide if Ctrl+C should "copy" or "copy picture data"

[d2phap]

Ctrl+C will be for "Copy image data" in the next version, also requested in #901