Add linear/angular getters for spatial terms of BodyNode

+ API change (as examples):
    + `BodyNode::getWorldTransform()` --> `BodyNode::getTransform()`
    + `BodyNode::getWorldVelocity()` --> `BodyNode::getWorldLinearVelocity()`, `BodyNode::getWorldAngularVelocity()`
    + `BodyNode::getWorldJacobian()` --> `BodyNode::getWorldLinearJacobian()`, `BodyNode::getWorldAngularJacobian()`
+ Fix #134