Fixed implicit conversion from Blink1Duration to TimeSpan

Implicit conversion from Blink1Duration to TimeSpan was not being calculated correctly.

I also updated the code so that the conversion will round to the nearest Blink1 update interval instead of always truncating the remainder. See ImplicitConversionToTimeSpan test.

For example:

253ms  = `Convert.ToInt32(253 / 10.d) == 25`
255ms  = `Convert.ToInt32(255 / 10.d) == 26`