Change log timestamp render format to "HH:mm:ss.fff"

[YevgeniyShunevych]

Currently log timestamp is rendered in a short time format, like "9:12 AM", which is not very informative. Usually test steps took milliseconds, sometimes seconds. And it is useful to see the time difference between particular steps. So I propose to render timestamp with "HH:mm:ss.fff" format. For example, "9:12 AM" becomes something like "09:12:45.125".