uTP rethink / rework / remove(?) the clock drift calculator in uTP

[kdeme]

There are currently some issues with it, see #726

After going through that code it seems there are still issues but feels very tricky to fix in its current form. I'm not sure if the idea behind it (e.g. this magic value of -200000 at which point penalties are applied) actually is effective.

So in general i think this can/should be simplified, if it is even needed at all.