added first draft of C-API, btConvexHullShape takes float* instead of btPoint*, added getGravity to btRigidBody

Demos/OpenPL_Demo/OpenPL_Demo.c

@@ -0,0 +1,44 @@
+
+#include "Bullet-C-Api.h"
+
+
+int main()
+{
+	float timeStep = 1.f/60.f;
+
+	/* initialize */ 
+	plPhysicsSdkHandle	sdk = plNewBulletSdk();
+	
+	plDynamicsWorldHandle world = plCreateDynamicsWorld(sdk);
+
+
+	float radius = 1.f;
+	plCollisionShapeHandle collisionShape = plNewSphereShape(radius);
+
+	void* user_data = 0;/* can point to a graphics object */
+
+	float mass = 1.f;
+
+	plRigidBodyHandle body = plCreateRigidBody(user_data, mass, collisionShape );
+
+	plAddRigidBody(world, body);
+
+	
+	
+	plStepSimulation(world,0.1f);
+
+	/* cleanup */
+
+	plRemoveRigidBody(world, body);
+
+
+	plDeleteRigidBody(body);
+
+	plDeleteShape( collisionShape);
+
+	plDeleteDynamicsWorld( world);
+
+	plDeletePhysicsSdk(sdk);
+
+	return 0;
+}