ENH: Make the behavior of increase_range and decrease_range methods of LargeRangeEditor more userfriendly.

Currently the increase/decrease_range methods of LargeRangeEditor will increase/decrease the current slider range (cur_low, cur_high) by a factor of 10,
and set the new value of the trait to min(max(cur_low, value), value, cur_high). This means that if you push the buttons to increase the range once and then immediately decrease the range once the value of the trait is not the same value as when you started.
This is unexpected. I would expect the value to be same as when you started (given that the value did not exceed the boundaries low and high). If the increase/decrease method also increased/decreased the trait value of a factor 10, it would solve the problem and make the behaviour more user friendly.