[dartpy] Add JacobianNode and operational space controller example

[jslee02]

The operational space control now can be written as easy as a few lines of Python code:

class HelloWorldNode(dart.gui.osg.RealTimeWorldNode):
    def __init__(self, world, kr5, target_pose = [0.3, 0.3, 0.3]):
        super(HelloWorldNode, self).__init__(world)
        self.kr5 = kr5
        self.dofs = self.kr5.getNumDofs()
        self.ee = kr5.getBodyNode('palm')
        self.target_pose = target_pose
        self.Kp = np.eye(3) * 50.0
        self.Kd = np.eye(self.dofs) * 5.0

    def customPreStep(self):
        M = self.kr5.getMassMatrix()

        J = self.ee.getLinearJacobian()
        Jt = J.transpose();
        JJt = np.matmul(J, Jt)
        kI = 0.0025 * np.eye(3)
        invJ = np.matmul(Jt, np.linalg.inv(JJt + kI))

        dJ = self.ee.getLinearJacobianDeriv()
        dJt = dJ.transpose()
        dJdJt = np.matmul(dJ, dJt)
        invdJ = np.matmul(dJt, np.linalg.inv(dJdJt + kI))

        e = self.target_pose - self.ee.getTransform().translation()
        de = -self.ee.getLinearVelocity()

        cg = self.kr5.getCoriolisAndGravityForces()

        tmp1 = np.matmul(np.matmul(invJ, self.Kp), de)
        tmp2 = np.matmul(np.matmul(invdJ, self.Kp), e)

        forces1 = np.matmul(M, tmp1 + tmp2)
        forces2 = cg
        forces3 = np.matmul(np.matmul(np.matmul(self.Kd, invJ), self.Kp), e)

        forces = forces1 + forces2 + forces3

        self.kr5.setForces(forces)

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• Document new methods and classes
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• Set version target by selecting a milestone on the right side
• Summarize this change in CHANGELOG.md
• Add unit test(s) for this change

[codecov]

Codecov Report

Merging #1323 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1323      +/-   ##
==========================================
+ Coverage    57.1%   57.12%   +0.01%     
==========================================
  Files         366      366              
  Lines       27050    27050              
==========================================
+ Hits        15447    15452       +5     
+ Misses      11603    11598       -5

Impacted Files	Coverage Δ
dart/dynamics/EulerJoint.cpp	70.73% <0%> (+3.04%)	⬆️