Merge branch 'master' of github.com:AndreaCattaneo/atk into develop

* 'master' of github.com:AndreaCattaneo/atk:
  composer
apply bootstrap theme at panetabs and avoid 'Array to string conversion' notice
fix missed close ol tag in theme bootstrap
Merge branch 'develop' of https://github.com/Sintattica/atk into develop

* 'develop' of https://github.com/Sintattica/atk:
  Added "reverse_attributeaccess_logic" global configuration variable
add support for nested forms ( used in atkOneToManyRelation with flag AF_READONLY )
apply translation at menu label
Spinner on action buttons