Added activatable component, which allows a button to cause secondary activations to occur while an object is grabbed. Also made the pen "sticky" so it stays attached to your hand when you grab it. It can then only be dropped by using the "primary" grab button (e.g. grip buttons). The triggers now are "secondary_action" buttons, which work like normal except in the case that you are holding a sticky object, in which case they will not cause the object to be dropped.

Added drawing of "caps" to the start/end of each line drawn; cleaned up and reorganized code; light optimization pass