function getClipboardContent(clipboardEvent) {
			return getDataTransferItems(clipboardEvent.clipboardData || editor.getDoc().dataTransfer);
		}
Gets various content types out of the Clipboard API. It will also get the
plain text using older IE and WebKit API:s.

@param {ClipboardEvent} clipboardEvent Event fired on paste.
@return {Object} Object with mime types and data for those mime types.