fix #513 $constructor, $destructor consistency refactoring

Adding the possibility to use $constructor when calling a parent constructor.
fix #135 undefined element in View

added a check when creating a view with an undefined element,
we now log an error.

Close #514
fix #525 null and undefined are not callbacks

aria.utils.Type.isCallback(null) and aria.utils.Type.isCallback(undefined)
fail instead of returning false
refactor moving templateTests/features

Close #519
Addition of tests on the aria:Dialog widget