[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

Add no-viewer mode and tests

Re-initialize startState_ and endState_

Add parameter for context in rbprm builder and fullbody