CanvasOnChain: Create a SmartContract that stores the pixels

[melanke]

Create a contract that stores the pixel coordinate, the author of the pixel placement and the color of the pixel.

We should only have a few color options.

Remember to validate the position of the pixel and if the color is valid.

When the contract is deployed it needs to already have a default drawing, something related to Batch11

[melanke]

Its not supposed to be a discussion.