Fix setting sliders skipping values

Another important discovery. The difficulty slider can't be set to 6, 18, -40 or -46: it goes straight from 5 to 7 and so on. Integer sliders were turning the position into a float and back, and the cast truncated values like 5.9999924 down to 5.

Integer sliders now just use min + pos. No more floats. They only went through the float path because difficulty used to be a Float slider.

The actors processing range slider was also one position short (Range 3584 for 3584..7168) and skipped 7166. With the new code the default 7168 wouldn't fit at all, so it's 3585 now.

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