[BUGFIX stable] Fixes issues with unescaped strings `{{{x}}}`

This Fixes #9805 in stable and should work in beta as well.
There is a separate fix for canary that has also been submitted
where the structure has changed for HTMLBars.
[DOC beta] An attempt to update the Ember.run.bind docs per #9735
[BUGFIXE beta] Close #9542 by re-throwing synchronous errors
[BUGFIX beta] Route.send is unit testable

this.router doesn’t exist when unit testing
Ember.Route, and hence .send breaks all the time;
this change allows you to unit test routes and
their actions even when this.router is absent.

/cc @rwjblue

Conflicts:
	packages/ember-routing/lib/system/route.js