Add ascii-art representation of line quality

[burrscurr]

It would be cool to not simply return an aggregated measure (for instance a single number), but visualizing deviations of the line as ascii art. This could look like this:

Maximum deviation: 25.5 meters

                  #                                             
    #  ##        ##                                 ##   ##  #  
  ### #### #  # ####  ##                      #    ###   ### #  
 ########### ############       ## # # ## ## #### ##### ####### 
 ###############################################################
|                                                               |
| <- line start                                     line end -> |