Reset problem when robot is loaded, not when calling ProblemSolver::solve

  Formerly, until calling method solve, additional obstacles where not taken
  into account.
Cosmetic changes

  - re-indent files before inserting directed roadmap,
  - delete trailing white spaces.
Make possible to use no path optimizer.
Move test of existence of a path from PathPlanner to Roadmap.
Implement oriented roadmap

  - new implementation of connected components.
Move graph-connected-component.hh to src.

  User do not need this class.
Rename CCGraph -> ConnectedComponentGraph.
Simplify insertion at end of list.
Add methods to simplify management of connected component,

  - when creating a new node and connecting it both ways to another node, the
    new node is simply added to the connected component of the previously
    existing one.