increase default process number for serve-develop and use threading when debug is enabled
increase default process number for serve-develop and use threading when debug is enabled

Anderson0026/mapproxy,procrastinatio/mapproxy,camptocamp/mapproxy,mapproxy/mapproxy,kaiCu/mapproxy,geoadmin/mapproxy,drnextgis/mapproxy,olt/mapproxy,vrsource/mapproxy,procrastinatio/mapproxy,camptocamp/mapproxy,Anderson0026/mapproxy,mapproxy/mapproxy,vrsource/mapproxy,drnextgis/mapproxy,faegi/mapproxy,geoadmin/mapproxy,faegi/mapproxy,olt/mapproxy,kaiCu/mapproxy