Plugin subsystem: Use entry_point.dist to fetch metadata
Plugin subsystem: Use entry_point.dist to fetch metadata

Support egg "PKG-INFO" and wheel "METADATA" files in metadata folder. Less
guess work throughout the include path this way.

Better solution for #2625 than c3eebdb

foosel/OctoPrint,Jaesin/OctoPrint,Jaesin/OctoPrint,foosel/OctoPrint,foosel/OctoPrint,Jaesin/OctoPrint,foosel/OctoPrint,Jaesin/OctoPrint