use write_atomic in seed.ProgressStore (closes #162)
use write_atomic in seed.ProgressStore (closes #162)

vrsource/mapproxy,procrastinatio/mapproxy,procrastinatio/mapproxy,olt/mapproxy,olt/mapproxy,mapproxy/mapproxy,camptocamp/mapproxy,vrsource/mapproxy,camptocamp/mapproxy,mapproxy/mapproxy,drnextgis/mapproxy,drnextgis/mapproxy