Tune effect of motion on KF/GF boost in two pass;

This code adjust the impact of the amount and speed of motion
on GF and KF boost.

Sections with lots of slow motion will tend to have a
somewhat bigger boost and sections with fast motion may
have less.

There is a knock on effect to the selection of the active
quantizer range.

This will likely require further tuning but helps with a couple
of particularly bad edge cases.

Change-Id: Ic2449cda7305672b69acf42fc0a845b77ac98d40