Add option to enable/disable biome map rendering at low zoom levels

Since Chunky is primarily rendering software, and is no longer intended to be used as mapping software, viewing the biome map is not particularly helpful in most cases. Instead, the block map may be more useful, even when zoomed out greatly.

Start by locating the low-zoom biome map rendering behavior and any existing map display options or controls. Define the option's enabled and disabled behavior, then verify that the block map can be shown instead at greatly reduced zoom levels.

Written by the indexing model from the issue text.