Correct awkward keyboard entry of Camera Exposure

[tom131313]

Camera Exposures may have a minimum non-zero value such as LifeCam is 5 and OV9281-110 is 7.

Allow easy typed entry of exposure numbers that don't start with the minimum value digits. [Referring to the keyboard entry field to the right of the range slider.]

For example, if you want to enter the value 24, you cannot type a digit less than 7 over the 7 (for the OV9281). To type a value of 24 one awkward way is to type after the 7 making 724 and then backspace to the 7 and delete it.

Recommend allowing entry of any value directly. This may necessitate allowing briefly a blank, null, or zero value.