[bugfix] Properly bind the exposed on/off/emit functions

[vincentfretin]

Be sure the exposed on/off/emit on Inspector are bound to Events so an event emitted with AFRAME.INSPECTOR.emit is correctly catched in an Events.on listener, otherwise it's using two different registries and doesn't work.

And example of usage of emit externally for a component to trigger the update of the scene graph.
3DStreet/3dstreet@6990401

[vincentfretin]

Closed in favor of #755
I changed my mind, the usage of AFRAME.INSPECTOR.emit('entitycreated', el) externally is wrong. The SceneGraph should be fixed to listen on child-attached/child-detached to update.

[vincentfretin]

I reverted the above mentioned change in 3dstreet and did this instead 3DStreet/3dstreet@5ac90b7
I'll do a similar change for aframe-inspector. This fixes showing in scene graph entities created by a component you add.