Movable cursor in menu text fields

[Matt]

Minor quality-of-life improvement.

Right now in the menus you can only hit backspace or type, if you typo or otherwise need to change something at the very start of a longer string you're SOL and have to delete and re-type everything that was placed after the typo. Would be nice if it worked more like the console line where you can move the cursor back and forth to delete or insert as needed.