Make some LocalIdList methods const

Change some methods of the class LocalIdList to const, so that they can
be called on a const object. These methods are: localToGlobalId,
globalToLocalId, size, containsBodyPart, containsId and toString.
Testing locomotion control on iCubSim

- implement management of variable size member variables (not tested
yet)
- add estimation of joint velocities
- add printCountdown varible to print debug information at a rate
different from the Thread's rate
- add computation of world-base rototranslation assuming left foot is
fixed
- add preStart and preStop operations
- add selection matrix S for selecting active joints