Add button to max out goal input

[vinnydiehl]

I'm picturing a little chevron in the upper-right corner of the input, that can be used to max out the goal for that input. Normally 252 (and should in fact always choose 252, even in generations that allow 255), but would be especially useful when nearing the 510 limit; it would do the math and fill in the missing number to reach that limit exactly.