Two small improvents for still OCR


Here's two small changes which would improve my experience using the still OCR:

1. This has been requested on this forum before around two years ago, it would be nice if the still OCR could open images from the clipboard directly or if we could use Pleco as a target action for images.

2. The mostly transparent grayish background of the selection rectangle should be configurable like the other colors, personally I think it's a little annoying since it reduces the contrast of the text I am reading and is not really necessary, the green rectangle is already pretty obvious.