Use Mantle version of Class, eventemitter and View

Add dependencies to ext.mantle.oo (which uses oojs EventEmmiter)
and ext.mantle.views
instead of shipping our own.

* Remove support for event namespaces
* Adjust Router/EventEmitter inheritance

Bug: 67107
Change-Id: Ib6ae25eafc32d8a8fc295c58a97f32bc50d0fcbd
Merge "Use Mantle version of Class, eventemitter and View"