Allow to configure the name of the onload function

[iambrosi]

For example:

<script src="https://www.google.com/recaptcha/api.js?onload=myOnloadFunction&render=explicit" async defer></script>

var app = angular.module('myModule', ['vcRecaptcha']);

app.config(['vcRecaptchaServiceProvider', function(vcRecaptchaServiceProvider) {
    vcRecaptchaServiceProvider.setOnloadFunction('myOnloadFunction');
}]);

[TheSharpieOne]

What is the need/use case for this? To prevent overlap on the global/window scope?