Revert "require PIL only if it is already installed, otherwise require Pillow"
Revert "require PIL only if it is already installed, otherwise require Pillow"

Pillow needs some more work. Use PIL for now as the standard.

This reverts commit 57bc3d4b10c7437b52194b61146b32e3f1895afc.

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