--check-tiles is now activated by shrinking maps
better detection for --forcerender situtations
Also cleaned up some docs and comments
Moved tiledir creation to TileSet constructor
biomes are no longer relevant, it's handled automatically.
Also rendering a live map is not a problem these days, with the retry
code it rarely causes issues.
Added all about the new config file format. Needs checking for accuracy.
Also need to update the faq and other sections of the docs now that the
options page is gone.