Context menu actions for images in Resources tab of inspector use blob: instead of original URL

Doing so breaks action that copies URL to clipboard (`blob:` is useless outside of WebKit) and breaks windows opened from inspector.
Also it breaks drag and drop.
We can also consider these two items:
 - allow to set policy for opening these resources, similar to `QWebPage::​LinkDelegationPolicy`;
 - add action to copy image data as `data:` URI (available in Chromium).