Bugfixes and polish - MASA LIFE 1.2 release

- Overhaul of `dtCollisionAvoidance`: parameters moved to the behavior itself and better documentation.
- Overhaul of `dtPathFollowing`: parameters moved to the behavior itself, target setting moved to the params and better documentation.
- Clearer lifetime for agents desired velocity.
- Renaming of dtVperp2D tp dtVCross2D for better consistency.
- Renaming `dtCrowd::setAgentBehavior` to `dtCrowd::pushAgentBehavior`.
- Renaming `dtCrowd::updateAgentPosition` to `dtCrowd::pushAgentPosition`.
- Renaming `dtCrowd::applyAgent` to `dtCrowd::pushAgent`.
- Addition of the *mazy hall* DetourCrowd sample.
- Additional DetourCrowd unit tests.