Add mentions of bioformats_package
Merge pull request #646 from sbesson/grid_templates

Improve server-template description in advanced configuration
Replace all occurences of PIL/Python Imaging Library by Pillow

As of 5.0.0, we start using Pillow as the default imaging library for Python.
This commit makes the corresponding changes under the existing documentation
pages.
Add section to server upgrade page about Pillow/PIL
Fix Pillow downloads page URL
merge dev_5_0 -D org -I include -E exclude: PR 640 (Update docs for import and logging fixes)
merge dev_5_0 -D org -I include -E exclude: PR 651 (11955 loci-tools docs)
merge dev_5_0 -D org -I include -E exclude: PR 653 (Update documentation to use Pillow instead of PIL)