Update API to load robots

ServerManager: use version from hpp-corbaserver is available

[Python] update to change in loadRobotRomModel and loadRobotCompleteModel, init now load the robot if required

Replace @ with dot operator

  for compatibility with python2.

[Python] add erasePreviousState argument in interpolateConfigs

Otherwise, if a test fails, an exception is raised, and `process.kill()`
is never called.

Update README.md

fix setStartState/setEndState for 3D contacts

fix surface extraction from guide