Add optional Grove-compatible connectors to IO boards

[kripton]

Seeed studio provides an "Grove DMX module" (https://wiki.seeedstudio.com/Grove-DMX512/) which is basically an RS-485-driver + 3-pin XLR connector. It's not cheap, it's not 5-pin and it cannot do input or RDM. However, we could support it by adding Grove-compatible connectors to the IO boards (before the RS-485 driver).