Merge pull request #23 from ANfactory/master

[js] corrected the way to count items in  FormCollection.addItem
Adding a new option "pathCallback" on @SnowcapCore\File annotation

 Allowing the dynamic generation of the path through a public method of the Class where the Annotation is used.
 Adding checks on required annotation option in the FileSubscriber
 Updating code to replace deprecated methods
[Tests] Fixing Navigation and Google twig extensions to pass the tests
add getActivePaths in NavigationExtention