[RFR] Fix BC issue with step attribute

[jpetitcolas]

Adding float type introduced a backward compatibility issue. As new ma-input directive now has a ng-attr-step attribute, it skipped the step attribute set through the Field.attributes() method.

This PR fixes it, allowing the following code:

nga.filter('count', 'number').attributes({ step: 'any' }).format('0.000');

To be equivalent to:

nga.filter('count', 'float');