fix collection remove event

dispatch ``remove.mopa-collection-item`` with ``triggerHandler`` rather than ``trigger`` to prevent removal of the whole collection. from jQuery docs:

> Note: For both plain objects and DOM objects, if a triggered event name matches the name of a property on the object, jQuery will attempt to invoke the property as a method if no event handler calls event.preventDefault(). If this behavior is not desired, use .triggerHandler() instead.

because events dispatched with ``triggerHandler`` don't bubble, one needs to listen for this event on the collection control group.