Explore replacement of pymclevel with local equivalent

[mathuin]

I use very few of the pymclevel features.

Some constants I take from pymclevel:

• max level height
• chunk width
• names and values for blocks

The methods I use:

• retrieve bounds of world (buildmaps)
• create worlds (buildregion, tiles)
• copy blocks and data from one world to another (buildregion)
• save worlds (buildregion)
• create chunks in region (tiles)
• set block and data at location (tile, ore, tree)
• get block and data at location (ore)

Right now, each tile is a Minecraft world. It may be worth changing tiles to work as arrays first to see if this saves time.