fixing some (pre-)translation issues

and a logical flaw
I believe this will raise an expectancy that it will not fulfill. On the other hand "vertical raster" doesn't raise any expectancy at all since it's not understandable... 
Just to make it clear to whoever will read this, these buttons are making it possible to move elements by a given step from their original position. So the "grid origin" is different for any elements, it's not a grid for the page. meaning a two staccatos on two different pitched notes will *not* be aligned if the user moves them 3 grid steps up. I'm not sure how to convey this in the name of the action...