Allow Trait API clients to override and use initlialize method of TraitView class

Current behaviour: When traits get added with TraitView.addType method they are extend TraitsViewer.itemView(which is TraitView). When TraitSelectView class extends TraitView it overrides initialize(o) method and calls TraitView.prototype.initialize.apply(this, arguments); to initialize parent class(as i understand). This allows TraitSelectView to override some initializing logic. For example override this.tmpl and use custom template for a trait

For a custom trait with overridden initialize method there we gonna see an error:

editor.TraitManager.addType('attrNoVal', {
   initialize (o) { console.log('TEST') },
})

But with the following code everything works perfect and i can override a this.tmpl and do other things dirty :) things:

editor.TraitManager.addType('attrNoVal', {
initialize (o) {
      // Dirty hack :) But it works
      editor.TraitManager.getTraitsViewer().itemView.prototype.initialize.apply(this, arguments)
    },
})

Expected behaviour: Allow Trait API clients to override and use initlialize method of TraitView class so we can easily customize initializing logic of a trait