Introduced the light entity form type

It allows to provide choice list of entities without hydrating all the
entities of the collection. It delegates the choices list generation to
the entity repository which then can provide an array of id => label.
Merge branch 'master' into prevent-hydrating-all-families
Fixed php CS
Updated changelog
Handle multiple choices in the light entity form type
Prevented reverse transforming non array when multiple is true
Translated family choices
Sorted attribute choices by label and group label
Escaped reserved yaml character
Fixed broken scenario after family code formatting
Merge pull request #737 from akeneo/prevent-hydrating-all-families

Introduced the light entity form type