Enhanced documentation of Screenshot library.
Enhanced documentation of Screenshot library.

Update issue 1225
Documented that taking screenshots requires a display.

waldenner/robotframework,waldenner/robotframework,fiuba08/robotframework,fiuba08/robotframework,fiuba08/robotframework,waldenner/robotframework,fiuba08/robotframework,ldtri0209/robotframework,fiuba08/robotframework,waldenner/robotframework,ldtri0209/robotframework,ldtri0209/robotframework,waldenner/robotframework,ldtri0209/robotframework,ldtri0209/robotframework