Added rudimentary hexagonal renderer

[AndreRenaud]

This is very simplistic, and due to the limited rendering order options at the moment it has some visual artifacts. However it does render things in a reasonable manner to the screen.

[lafriks]

Can you add some small sample map to test this with?

[AndreRenaud]

I've pushed a map, which made me realise that I'd only done the Y orientation. There are some caveats here, and this is very simplistic, but hopefully sufficient to start with.

[AndreRenaud]

Hey - just pinging this PR to see if theres anything more you'd like me to do to hopefully get it merged?

[lafriks]

I had not yet time to test it, will do it soon