Made EngineThrustController More Lightweight. Operations should be less
performance-intensive. Changes made:

 - SetPercentage directly manipulates engine thrust limiter
 - GetPercentage returns engine thrust limiter
 - AdjustPercentage adjusts engine thrust limiter by a given amount
 - (Fx updates are handled by the engine itself)
 - Changed "Group2" event title to "Group2"
 - BindEngine method only binds when the engines are not yet set
 - removed increase/decrease initial thrust system, since this is
       available using thrust limiters.

Consequences of these changes:

 - SetPercentage only has to be called when a change is required
 - Thrust limiter value is stored persistantly by the engine itself