Engine 3.91 for all games from now on

After seasonrollover we usually activate new features inside the simulation engine we have tested for one or more seasons when simulating non-official games.

This time we made the following changes / improvements available for all gametypes:

- improved fumble returns
- less time consumption per play
- much less time consumption per play during the last seconds of each half

There were a few bugfixes as well, as every season.

Now, don't forget to adapt playbooks if needed. Keep in mind: we are simulating kind of a No Huddle Offense during the last around 75 seconds of each half.