PIM-2115 : add missing group by in selector, for now if a product is in
many groups we have a wrong number of lines
Don't show currency in grid for price attributes if the value is null
Merge pull request #782 from akeneo/fix/PIM-2115

PIM-2115 : add missing group by in selector extension
Cleaning up the README.md as installation docs is more exhaustive
Merge branch 'master' of github.com:akeneo/pim-community-dev
Fixes styles
Merge branch 'master' into bugfix/pim-2110