Buildings and infrastructures

[gaelysam]

Following a discussion I had recently with someone aiming to recreate a city in Minetest, I'm considering adding an optional "building" layer. This needs work on 3 places:

• In the Python code, to transform a vectorial map into an array
• In the GUI
• In the Lua mapgen

This needs to be done quickly since this person would need this map for an event on April 14th.
(EDIT: GUI)