Refactor distance functions

This is a minor refactor of some of the line drawing routines as well as a minor tweak to the way the marks are shown/removed. I also changed the default clear distance from 5 to 100 since basically everything in the game is at least 5m away from you at any given time.
* Changed marks to no longer fade in/out
* Broke the line drawing function out to a separate method
* Added a closure to calculate the distance to the player for arbitrary units
* Changed default clear distance from 5 to 100