Add HTMLBars version of makeBoundHelper.

* Add HTMLBars version of `makeBoundHelper` (much simplified).
* Add HTMLBars version of `helper` (makes a bound helper from either a View or function).
* Deprecate `Ember.Handlebars.makeBoundHelper`.
* Deprecate `Ember.Handlebars.helper`.

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Added deprecation for `Ember.Handlebars.makeBoundHelper` in favor of the new helper.
Confirm, @mmun and I talked through a strategy to handle this at the hooks level. We should review at the next HTMLBars meeting.