Add root joint type and root joint name in python class Robot

  - useful for displaying in rviz.
Fix implementation of Problem::createPositionConstraint.
Implement interface method Problem::createOrientation constraint.
Implement method Robot::shootRandomConfig.
Merge branch 'master' of https://github.com/florent-lamiraux/hpp-corbaserver

Conflicts:
	idl/hpp/corbaserver/problem.idl
	idl/hpp/corbaserver/robot.idl
	src/problem.impl.cc
	src/problem.impl.hh
	src/robot.impl.cc