Allow to set modalClass with full namespace or as directly a function

Currently, we can define a modal class as shown below:

// The modal class implementation

abp.modals.MovieCreation = function () {
     this.initModal = function(modalManager, args) {
        console.log('initialized the modal...');
    }
};

// Modal manager instance

var newMovieModal = new abp.ModalManager({
    viewUrl: '/ModalWithForm',
    modalClass: 'MovieCreation'
});

We can support so that we directly pass the function to the modalClass parameter:

var newMovieModal = new abp.ModalManager({
    viewUrl: '/ModalWithForm',
    modalClass: function () {
     this.initModal = function(modalManager, args) {
        console.log('initialized the modal...');
     }
   };
});

or we may define the function in my.customns namespace instead of abp.modals and pass it as full form:

var newMovieModal = new abp.ModalManager({
    viewUrl: '/ModalWithForm',
    modalClass: `my.customns.MovieCreation`
});

Start with the ModalManager implementation and trace how its modalClass option resolves the existing abp.modals.MovieCreation name. Check how the option is used during modal initialization, then verify that a fully qualified namespace string and a function value both initialize the modal as shown in the issue.