More markers!

[zachwaffle4]

This adds 3 markers:

1. duringLast(a: Action) executes a during the last trajectory segment; equivalent to afterTime(0, a)
2. untilTime(dt, a) executes a dt seconds before the last segment is supposed to end
3. untilDisp(ds, a) executes a at a displacement ds before the end of the last segment

Closes acmerobotics/road-runner-ftc#15

[zachwaffle4]

yes that last commit has nothing to do with markers i just didn't want to make a whole separate pr for one line of code

[kevinthegreat1]

I just coded this without checking open prs...

But I have a few questions, I believe afterTime and afterDisp works on the current/next trajectory segment, not the trajectory/last segment. (I think the documentation is confusing, but based on the code and observed behavior, it runs during the current/next trajectory segment, which is the same as time passed since the previous trajectory segment.)

Based on how afterTime and afterDisp currently work, I would expect untilTime and untilDisp to run a certain time or distance before the end of the current trajectory segment, not before the end of the trajectory/last segment.