Copy mapfile automatically, by name (Feature) about hematite

[toqueteos]

This should be quite easy to do right now. It may happen sooner than you think... 😄

[mattico]

I can do this once I'm done with #260.

If I'm understanding correctly, the first part works already e.g. hematite Test loads the map named Test from the minecraftdir. It doesn't copy the save though (is that necessary?)

The second part does sound like a good idea, though I think it should require an argument or an invalid world to be given as its a convention for no-arguments to print usage.
Example:

$ hematite --list-worlds
./Test
./Test2
~/.minecraft/saves/Test3

$ hematite Test4
No save `Test4` found. These saves were found:
./Test
./Test2
~/.minecraft/saves/Test3

[mattico]

I'll do this once I'm done with #203 😆