SHORTEST_PATH: path enough far away from walls with small vertices

- changed vertice mechanics and added logic to adding and removing
  walls. bool hasWall is true when there is a wall within vertices
  area. bool blocked is true when there is a wall within vertices
  area or nearby.
- now lines in pathLines_ are added to scene in usePath and removed
  after roomba reaches goal point (in sensorUpdateTimerTimeout)
- not tested with roomba