[MapProxy] Using GMaps-style numbering for disk caching

[Paul Norman]

I have a lot of TMS sources, some pre-tiled on to disk. 

It would be useful if I could have the cache layout on disk for a disk cache
correspond to google/openstreetmap TMS layout. Is this possible?

I've thought about defining a grid for the cache, but I've just been
treating caches as a black box so far and don't really understand how they
work.

I've been using GLOBAL_MERCATOR or one defined with a different number of
zooms, but that's the extent I've used grids so far.