Use a dictionary to specify joint mapping.

Remove l_ankle for now.
Remove method initializePr2.
Reintroduce left-ankle, correct the wrist/gripper frames.
Cleanup prologue.
Add tasks in pr2 tasks, homogenize solver initialization.

The solver initialization method is now closer to the one
in application, and creates the additional shortcuts in the
robot python class.
Add a task for the chest.
Add a task for the position.
Remove the use of the operational point for the hands.
Add a simple test for the pr2, to check the position of the end effectors with rviz.