[pkg] Depend on Pillow instead of PIL
The Pillow library is becoming the de-facto replacement for PIL.
It also is way simpler to install with pip than PIL.
Closes #4411354.
include *.pyinclude */*.pyrecursive-include data *.gif *.png *.ico *.css *.jsrecursive-include i18n *.porecursive-include wdoc *