Improvements for setting up grids

[LapisLettuce]

Possibly make grids patternable? Like if I set up the front 2 rows on a track, allow me to copy that pattern and extend it back by inputting a command. And idea for that could be:

/t set gridpattern <grid pos. 1> <grid pos. 2> <grid pos. 3> <# of checkpoints to be added>

Where:
<grid pos. 1> is first grid spot selection
<grid pos. 2> is second grid spot selection
<grid pos. 3> is a third grid selection where grid spots will start to be added from

For this command, all checkpoints with a higher value than <grid pos. 2> will be deleted and TimingSystem will start creating checkpoints starting from where <grid pos. 3> was in the same pattern and facing the same respective directions as was selected from <grid pos. 1> to <grid pos. 2>.