Translate directive and ngMessage not working

[crisbeto]

As mentioned in #702 the translate directive doesn't work when on the same element as https://docs.angularjs.org/api/ngMessages/directive/ngMessage.

Here's a simple example that breaks:

<form name="form">
    <input type="email" ng-model="email" ng-required="true" name="email" />

    <div ng-messages="form.email.$error">
        <div class="form-error" ng-message="required" translate="FIELD_REQUIRED"></div>
        <div class="form-error" ng-message="email" translate="EMAIL_INVALID"></div>
    </div>
</form>

I've been playing around with it a bit and it turns out that the error is caused because both the translate and ngMessage directive have the same priority(0). If we set the priority of translate lower, everything works as expected.
Here's a monkey patch that worked for me:

angular.module('pascalprecht.translate').config(['$provide', function($provide) {
    $provide.decorator('translateDirective', ['$delegate', function($delegate){
        var directive = $delegate[0];

        directive.priority--;

        return $delegate;

    }]);
}]);

Note that I'm not sure what consequences reducing the priority might have, but from what I'm seeing it works fine. I've also tested with interpolation and translate-values.

[knalli]

I've added an additional option setter $translateProvider.directivePriority(0).

Defaults to 0 just like AJS default.