(no motor support or advanced settings yet)
added btStaticPlaneShape serialization
Added toggle in cmake for BenchmarksDemo to enable/disable graphics rendering
Constraints reworked - all of them could now work with one or two bodies
Modification of constraint frames and initial positions of rigid bodies
now allowed at start frame only
Plugin version is set to 2.76
Turned on by default, use m_useOffsetForConstraintFrame = false to use old setup
Use "O" (capital 'o') button to toggle it in SliderConstraintDemo and ConstraintDemo
Total applied impulse copied back from btSolverConstraint to btTypedConstraint
1) Add fast branchless SIMD support for constraint solver (Windows only until we get other contributions).
See resolveSingleConstraintRowGenericSIMD in Bullet/src/BulletDynamics/ConstraintSolver/btSequentialImpulseConstraintSolver.cpp
resolveSingleConstraintRowGenericSIMD can be used for all constraints, including contact, point 2 point, hinge, generic etc.
2) During this refactoring, all constraints support the obsolete 'solveConstraintObsolete' while we add 'getInfo1' and 'getInfo2' support.
This interface is almost identical interface to Open Dynamics Engine, to make it easier to port Dantzig LCP solver.
3) Some minor refactoring to reduce huge constructor overhead in math classes.
It leads to problems with certain compilers, when Bullet/src is located in a long pathname.
Keep include path starting with "LinearMath/, "BulletCollision/, or "BulletDynamics/
