add BCAP non-goals to introduction

[moneyball]

In our presentation, one of the first slides states non-goals for the project. Namely,

1. To take a perspective on whether bitcoin should change or how fast it should change
2. To advocate for any particular change
3. To be become a blueprint for how to change consensus

We should state these in the introduction of the project paper as well to be very explicit as some people have had knee-jerk reactions assuming ill intent or being misguided.