Remove event proxying from core

[tgvashworth]

Event proxying added complexity to Flight core and should have been done in userland with a mixin. 2 will remove it. 1.x will continue to support it.

We'll publish a mixin that adds this, probably as this.(un)proxy.

[tgvashworth]

Landed in 1f3203d, but we also need a mixin the add this back via the API discussed above.

[tgvashworth]

I've submitted an issue on the new flight-toolbox repo to track the creation of this mixin: flightjs/flight-toolbox#1

[giuseppeg]

flight-toolbox++