refactored prices import
Fixed PHPDoc
Added metric family
Added unit tests
Merge branch 'master' into task/refactor_metric_import
Corrected metric validation
Fixed use statement
Fixed CI
Fixed PHPDoc
Fixed CS
PIM-1794: Fix after mergeing
Merge pull request #624 from akeneo/task/refactor_metric_import

Task/refactor metric import
Merge branch 'master' into PIM-1794
PIM-1794: Fix loading fixtures