Add screenshoter

I think it's would be useful.
It's capture image from the webView widget, uploads it on imgur and copy to clipboard direct link to uploaded file. I checked it on my Arch linux and it builds and working fine.
My C++ and Qt knowledge is very low so code may (should) contain some mistakes. Any comment and fixes are welcome.
This is a memory leak; wherever you have a `new`, you must have a `delete`, or the created object will remain in memory until the program terminates. Leak enough memory and you'll run out, causing a crash. Not good.

In this case, you don't even need a `new`; just:

    KVScreenshooter screenshooter;
    screenshooter.takeScreenshot(webView);

Would work just fine. A `KVScreenshooter` would get created on the stack, and destroyed when it goes out of scope. Alternatively, you could make the `KVScreenshooter` a member of the class, or a singleton (see `KVTranslator` for how that works). I don't know which is the best way, but I'd probably go for a member, then convert it to a singleton if that ever becomes more useful.