Muscodwalkin. Closes #72

Loads references from the centroidal solver, and runs ddp to track those references.

Some work still needs to be done to define properly the tasks (e.g., to add high cost velocity tracking on foot during contact transitions).

The current framework is meant to deal with multi-contact locomotion (and not just bipedal walking)

locomotion/centroidal_utils.py

@@ -2,7 +2,7 @@ import pinocchio
 import numpy as np
 from collections import OrderedDict
 from locomote import CubicHermiteSpline
-from crocoddyl import m2a, a2m, EmptyClass
+from crocoddyl import m2a, a2m
 from crocoddyl import CostModelSum,CostModelState,CostModelControl,CostModelForce,\
   CostModelFrameVelocity,CostModelFramePlacement,CostModelCoM,\
   ImpulseModelMultiple,DifferentialActionModelFloatingInContact,IntegratedActionModelEuler,\
@@ -80,7 +80,7 @@ def createMultiphaseShootingProblem(rmodel, rdata, patch_name_map, cs, phi_c, sw
   """
 
   #Define Cost weights
-  w = EmptyClass()
+  w = lambda t: 0
   w.com = 1e2;    w.state = 1e-1;    w.control = 1e-3;
   w.swing_patch = 1e4; w.forces = 1e-4;
   w.swingv = 1e4
@@ -207,7 +207,7 @@ def createPhiFromContactSequence(rmodel, rdata, cs, patch_names):
   N = len(t_traj)
 
   #------Get values of state and control--------------
-  phi_c = EmptyClass()
+  phi_c = lambda t: 0
   phi_c.f = OrderedDict(); phi_c.df = OrderedDict();
   for patch in patch_names:
     phi_c.f.update([[patch, np.zeros((N,6))]])