Add the start of a new GravityBlocks pattern. Only shows touched pixels in a random colour at the moment.

This pattern connected to a Node.js daemon which manages inputs from
multiple connected web clients. Currently, these web clients can touch
a square on an 8x8 grid, and these touches will be displayed on the
front face of the cube in a random colour.

Colour data is transmitted along with each touch, but it isn't used yet.

The pattern is currently single buffered, but conversion to double
buffered would be preferred.
Display incoming touches in the user's allocated colour
GravityBlocks server host:port should be passed in as an argument
Coloured dots on the front face of the cube leave trails going towards the back of the cube