waypoint simplification types: space -> underscore

[yakra]

For the waypoint simplification actions performed in the canonical_waypoint_name function, changing the names written to waypointsimplification.log to use an underscore rather than a space...

with space	->	with underscore
Straightforward concurrency:	->	Straightforward_concurrency:
Straightforward intersection:	->	Straightforward_intersection:
Exit/Intersection:	->	Exit/Intersection:
3+ intersection:	->	3+_intersection:
Exit number:	->	Exit_number:
Reversed border labels:	->	Reversed_border_labels:
Keep failsafe:	->	Keep_failsafe:

...would be more convenient when piping diffs to cut.

The 3 other actions, performed outside of canonical_waypoint_name, in the HighwayGraph constructor,
Appended region:
Revert to simple:
Appended !:
I think leaving the spaces in should be fine.

@jteresco, any objections?

[jteresco]

Sounds like a good idea to me, thanks.