nodecore clock [OPTICS SPOILERS]

an optical clock in [nodecore](https://content.minetest.net/packages/Warr1024/nodecore/). the bottom part is a loop that takes a while to disable its input, like minecraft clocks made with odd numbers of redstone torches. the top part is a rising edge trigger: it sends out a very short signal whenever its input starts being on. the idea is to use this for timing and sequencing in a machine.