Compute zmp from force sensors in the feet.

  Some initializations that used to be performed in this package were in fact
  application dependent. These initializations have been moved to the new
  package sot-application.
  - class solver has been removed,
  - features and tasks are not created anymore in AbstractHumanoidRobot class.

This commit remove files and references which are now in different packages.

  To trace all default signals, call AbstracHumanoidRobot.traceDefaultSignals
  method.

  This file is now defined by package sot-hrp2.

    This task contains the center of mass and ankles features.

    Both methods take a task as input and forward to Solver.sot.

Add support for additional frames storing sensors position, use it to compute HRP-2 camera positions.