Show custom spoil messages

[dlamkins]

We should allow module developers to show a custom spoil message when a module is spoiled. It is very disruptive when a module is spoiled and users are often confused about what they should do.

• We need to begin including spoil messages in our spoil.json.
• We will need to do this in a new spoil.json (spoil_v2.json?) as the additional data will be a breaking change (changing from string array to array of objects).
• Blish HUD will need to display this message in a clear way.

Blocked by blish-hud/SSRD#3