Add support for print parameters (palette and margins)

[marian-m12l]

On the firmware side:

• Send a "PARAMS" message before "PRINT" message
• Send status 0x08 after init command (was necessary for my test rom. there are other status codes but I don't know if official games check the status)
• Commented out some unused stuff

On the web UI side:

• Handle the "PARAMS" message to update the palette and margins
• Resize canvas according to margins and available pixel data
• Apply palette and margins

[marian-m12l]

Hi!
I added support for custom palette generation. To avoid coupling this with the printing parameters support, I'll make another PR with custom palette only.

[nezza]

This is awesome! Will test as soon as possible