Fix metadata download to remove historical aerial imagery

[kylebarron]

E.g. over Boston:

[kylebarron]

This is hard because the metadata on these images are Historical Topographic Maps and Historical Topographic Maps 7.5 x 7.5 Minute Map Series, exactly the same as the rest of the actual topographic maps. The file sizes are also about the same as the topo quads.

These images are showing up in "latest" because Boston doesn't have any topo maps created since the mid-1970s, which is when these images were taken.

So for now this isn't easy to fix.

[kylebarron]

The bulk metadata has a key named Orthophoto, which may be True for these images

[kylebarron]

As of https://github.com/kylebarron/usgs-topo-tiler/commit/edb221d668dcd1810d4ad510b981e38d5454049e, option for allow_orthophoto=False