Scrolling to selection doesn't work, and broken after reload

[Kuirtevich]

Hi. Our team have found two problems with the timepicker, which we thought were our improper usage of it, but finally they appeared to be issues of the script itself. I had to make changes in the script to fix them.

First, when you open a dropdown - it does not scroll to the selected value. First I thought this was just not intended to happen, but after analyzing the code, I saw that there is actually logic for it, but it doesn't work because it uses "ui" instead of "viewport" in _hasScroll() and in activate(). The first is not scrollable, while the second is.

Next, if we did ajax reload of the area containing the widget and the initialization script - this made it broken. The reason was in that "widget.viewport" was not assigned in the initializer - there is logic that skips initialization if the DOM element already exists. Also, for the same reason, events were not bound. In the end I have changed that part to remove and recreate the elements in this case.

You can check the updated version attached for more details. Sorry, I am totally new to GitHub, I think I might have collaborated, but I don't know how, and also not sure if this can be done better. So I'm providing this version just as an example. All changed parts are marked as "CUSTOM FIX".
timepicker_updated.txt