Missing features on Custom Level API

[yancouto]

Custom levels are working, though some features are still missing:

• Lasers/Emitters (probably need to figure out how they'd work in the custom level API).
• Checking if lava is burning or not
• Checking what the bot is holding
• Checking paint color on the floor
• Cannot recreate level "Cleanup on aisle 5", since we cannot create bodies. It could be done with buckets (maybe allow user to override bucket image? That's basically what we do on our code :P)
• Cannot recreate "Cleaner I" because the paint there is actually bleach, but that is just appearances, so maybe it is fine.
• math.random used on custom levels always returns different values. It should be fixed like the random in our levels (https://github.com/MarvellousSoft/MarvInc/blob/dev/marv/classes/reader.lua#L38)