[new content] block control

[ds-sloth]

A content creator requested the ability to make more customizable blocks, but a scripting API allowed to access blocks would be very expensive.

Relatedly, conveyor belt NPCs are slow and often cause significant gameplay slowdowns on low-end devices. It will be better to use blocks instead of NPCs for conveyor belts in future content.

Here are some steps we can implement during the 1.3.8 (1.8?) development cycle:

• [ ] add on/off and left/right conveyor belt blocks (4 blocks total), assigning myself for this portion
• [ ] allow SMBX events to call level Lua code
• [ ] allow Lua events to switch the color blocks, switch the conveyor belt direction, and toggle conveyor belt activation