fix: explorer sometimes does not find a path for a walkable target. There is nothing we can do then for now.

Added config param to disable path simplification (post-processing), new default is disabled simplification for navigating in complex surroundings

Also added circle check for current position; Print result interpretation when calling drive_to_POI_blocked

Added circle region around next way point for obstacle checking, until now, way up until waypoint was checked, not further, although robot has some radius when having reached this waypoint

Extend depth_occupancy_map to maintain a continuously updated map

See merge request !12

New obstacle check up to next waypoint, now taking all map entries into account not only last few laser scan points for replanning correctly with down projected RGBD points

Added threshold for only accepting possible obstacles with a minimum height in greater distances, avoiding to register ground points when camera isn't 100% correctly positioned in simulation

Added logic to  again clear map cells from downprojected obstacles, if there are ground measurements and viewing ray's angle to surface isn't too steep

Merge branch 'master' of gitlab.uni-koblenz.de:robbie/homer_navigation into dev/maintain_downprojected_map