Add `rasterio.env` block in each method to allow factory defined gdal config

[vincentsarago]

in #108 we introduced custom API route to wrap any gdal code within a specific environment. This worked well for python 3.7 but not for python 3.8. IMO adding a with rasterio.env(): block on top of each call to gdal (rio-tiler) code will make this easier.

How To

• add gdal_config in titiler.endpoints.factories.BaseFactory with default to dict
• add with rasterio.env(**self.gdal_config): on top of gdal blocks

[kylebarron]

This worked well for python 3.7 but not for python 3.8

Why not? Is the change here in Python, or rasterio, or GDAL?

[vincentsarago]

I think there is a change in python, I think adding the with rasterio.Env is less of a hack anyway!